ML19310A254
| ML19310A254 | |
| Person / Time | |
|---|---|
| Site: | Vallecitos File:GEH Hitachi icon.png |
| Issue date: | 05/23/1980 |
| From: | Bonilla M, Lienkaemper J, Tinsley J INTERIOR, DEPT. OF, GEOLOGICAL SURVEY |
| To: | |
| Shared Package | |
| ML19310A248 | List: |
| References | |
| 80-523, NUDOCS 8006060476 | |
| Download: ML19310A254 (36) | |
Text
..
,APPE!! DIX D e
UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY Surf ace f aulting near Livermore, California associated with the January 1930 earthquakes by M. G. Bonilla, J. J. Lienkaemper, and J. C. Tinsley 1
1 i
Prepared in cooperation with U.S. Nuclear Regulatory Ccanission l
i
't I
Open-File Recort 80-523 a
This recort is preliminary and has not been edited or reviewed for conformity with Geological Survey standards or nemenclature l
l
- Menlo Park, California
-1980' 80 06060Nih i
CONTENTS Abstract.................................1 Introduction...............................
3 Su rf ace F aul ti ng.............................
5 Main break within the Greenville f ault zone.............
5 Subsidiary breaks within the Greenville f ault zone..........
7 Other fractures within or near the Greenville f ault zone.......
8 Breaks within the Las Positas f ault zone...............
10 Relation of the January 1980 f aulting and fracturing to previously m a:c e d f au l ts...........................
13 Relatien cf the f aulting and fracturing to the earthquakes.....
14 S umm ar y.................................
15 R ef er en ces ci t ed.............................
13 i
l
i
.I s
i ILLUSTRATIO.'iS (all illustrations are at ba:k of reocrt)
Plate 1.
Surf ace f aulting near Livermore, Calif ornia, associated with the Janaary 1920 earthquakes.
Figure 1.
Index map showing locations of figures 2-5.
4 Figure 2.
Map shcwing fractures en Mines Road in relation to Las Pcsitas fault.
Figure 3.
Map shc ing fractures en Tesla Road in relation to Las Positas fault.
Figure 4 Map showing fractures on Vasco Road in relation to Las Positas f ault.
Figure 5.
Map showing fractures en Greenville Road in relation to Las Positas fault.
TABLES 4
Tacle 1.
F i el d o bs er vati ons........................ 19
ASSTp.ACT The earthquakes of 24 January (M 5.3) 1950 north of Livermore, s
Calif ornia, and 25 January '..i 5.2), were accompanied by surface faulting in 3
the Greenville f ault zcne and apparently in the Las Positas f ault zone also.
The surf ace f aulting was Of s::ntinuous and of small displacement.
The main ructure witf
- e Greenville f ault zone trended about N.3So'4.
It was at least 4.2 km 1:n; and may have extended southward to Interstate Highway 530, giving a pcssible length of 6.2 km; both of these lengths included more gaos thar: observed surf ace ructure.
Maximum displacements measured by us were ab:ut 25 m of right slip (including afterslip through 23 January); vertical comp:nents of as much as 50 m were seen locally, but these included gravity effects of unknown amount.
The main break within the Greenville f ault zones is very close to a f ault strand mapped by Herd (1977, and unpublished data).
A subsidiary brear. within the Greenville f ault zone was abou- 0.5 km.
long, had a general trend of N.450., and lay 0.12 to 0.25 km east of the 4
main break.
It was cnaracterized by extension of as much as 40 m and right slip of as trach as ?O mm.
This break was no more than 25 m from a f ault mapped by tier (un;ublished data).
Anther break within the Greenville f ault zone lay about 0.3 km scuthwest of the projection of the main break and trended about N330W.
It was at least 0.3 km long and shewed mostly extension, but at several places a right-lateral ecmponent (up t.c 5==) was seen.
This break was 80 to 100 m from a strand of the Greenville fault macced by Herd (1977).
Extensional fractures within the Greenville f ault zone on the fr:ntage roads north and south of Interstate Highway 580 may be related to regional extension or other processes, but do not seem to have resulted from faulting i
of the usual kind. One exception in this group is a fracture at the east side i
1
of Livennore valley which showed progressive increase in right-lateral displacement in February and March,1930, and is directly on the projection of a f ault in the Greenville f ault zone mapped by Herd (1977).
A group of more than 20 extensional fractures in Laughlin Road 1 km north of Interstate 580 probably are related to small tectonic displacements on f aults in the Greenville f ault zone.
They are adjacent and parallel to two f aults mapped by Herd (1977), are diagonal to the road, and most of them developed between 25 and 29 January, a period that included the M 5.2 shock s
of 26 January.
Observations at two locations indicate tectonic displacement on the Las Positas fault :ene as mapped by Herd (1977).
At Vasco Road a prominent break on a strand of the f ault showed about 0.5 =m of lef t-lateral strike slip on 7 February. An alinement array across this and other fractures at the locality indicates about 6 mm of left-lateral disolacement occurred between 21 February and 25 March.
On Tesla Road several right-stepping fractures, one of which showed 1.5 mm of left-lateral strike slip, lie on or close to previously mapped strands of the Las Positas fault zone.
The evidhnce at these two localities indicates that tectonic surf ace displacement occurred along at least 1.1 km of the Las Positas fault zone.
l l
l l
2
INTRODUCTION A::;t 11:C2 a.m.. 3 1:ific Standard Time on 24 January 1950 an earthcuake of se'1:a es ca 1: '.di ". 5.5* cc:urred about 17 km north of Liverm:re, 2
California, anc en 25 January about 6:30 p.m. local time an earthcuake M s 5.2" occur ed ab:ut a km north-northeast of Frick Lake and about 12 km southeast of the 24 January shock. When the location of the first shock was a::roximately known, reconnaissance teams of the U.S. Geological Survey began looking for surf ace f aulting and landsliding related to the earthcuake.
During the af ternoon of 24 January an aerial reconnaissance by small fixed-M = 5.75 ' O.03 (Std.. Dev. of Mean) was determined from 9 s
vertical-c:mpenent amplitudes with magnitude observations computed as described in U535 Earth;uake Data Rep:r:3 (5RG 6.2, KRA 6.1, SCG 5.S, NNA 5.3, COL 5.7, MAT 5.5, NUR 5.5, CAR 5.6, PMR 5.4.); data supplied by Jonn Minsch National Earthquake Informatien Service.
USGS Preliminary Determination of Epicenters (PCE) lists a bcdy-wave magn:cude M 5.3 and 5erkeley, a local b
magnitude M 5.5.
Reconstruction of two USGS short period vertical maxima L
give local magnitudes of 5.3 and 6.1 (J. P. Eaton, oral c:mmunication.)
M = 5.17 - 0.20 (Std. Dev. of Maan) frcm 3 abservations (5RG 5.5, HFS s
5.2, 3L a.S;
R a.4, not averaged.)
Vere ccmslete magnitude cata will be availaole in Earth uake Data Re: orts.
PCE M.
is 5.0.
Three observations of a
local magnitude from USGS short period verci:31 maxima are 5.4, 5.4 and 5.2 (J. P. Eaton, oral communication.)
U.C. 5erk'eley Seismographic Station reported a local magnitude of 5.3 using tne record of their strong-motion
" Wood-Anderscn"-type instrument.
3
wing plane was ccepleted by R. E. Wallace and M. G. Bonilla while ground reconnaissance was carried out by E. E. Brabb, E. H. Pampeyan, J. C. Tinsley, R. V. Sha-p, J. J. Lienkaemper, P. W. Marsh, R. C. Wils:n, D. K. Keef er, N. E.
Tannaci, and G. F. Wieczorek.
On 25 and 28 January at:i:i:nal reconnaissance was carried out and systematic mapping of surf ace f aulting began.
The ground reconnaissance on 24, 25, and 28 January c'uded examination of paved roads in the vicinity of the principal shocks of Za and 26 January; unpaved roads crossing the Marsh Creek and Morgan Territ:ry faults of 3rabc and others (1961) in sections 11, 14, 15, and 16 of T.1 S., R.1 E. (this through the courtes; of Mr. W. G. Morgan who provided both guidance and a four-wheel-drive vehicle); and the Concord f ault at points where tectonic creep has been occurring. Our reconnaissance along with information frc=
other investigators indicated the areas where more detailed work was required.
Systematic mapping was done intermittently frcm 25 January through 15 February, primarily by Sonilla, Lienkaemper, and Tinsley, but ably assisted at various times by R. V. Sharp, S. E. Carson, E. 3. Neaman, J. C. Yount, D G.
Herd, Rex Upp, M. J. Rymer, E. J. King, and S. F. Atwater.
Some field checking was also done 29 February and 1 April 1983.
d
SURFACE FAULTING The s.:rf ace f aulting associated with the earthquakes of 24 and 26 January was characterized by smali displacements, discontinuous traces, and difficulty in distinguisning some of it from landslide effects; nevertheless a main break and at least two subsidiary breaks were identified in the Greenville fault zene, and fracturing with progressively increasing lef t-lateral displace.ments in:icates f aulting in the Las Positas f ault zone also.
The following general descriptien of the faulting and fracturing makes use of the numbered locations marked on plate 1.
Details of field observations are given in table 1 for all locaticns except those numbered 33 to 25, which are fully described in the text.
Main break witnin the Greenville f ault zone One of the January 1950, breaks within the Greenville fault zone of Herd (1977) can be designated the main break on the basis of its close proximity to a major strand of the Greenville f ault zone (pl.1), its linearity, its length, and its right-lateral displacement (about 25 m) which was greater than on any other break.
The main break extended discontinously betwen the consecutively-numbered locations 1 througn 19, and probably to location 23 (pl. 1).
At its north end it consisted of two subparallel zones about 30 m apart extending about 0.1 km southeast from locations 1 and 2 respectively.
Between locations a and 5 no fault ruptures were seen.
Northeast of a line joining locatiens a and 5 are some short fractures that are probably related to slope movements, although one break shewed 6 m. of right-lateral separation combined with 27 m of extension. At location 5 two isolated en echelon left-stepping fractures in a dirt road indicate right-lateral displacement, but we were unable to measure the amount.
5
Between locations 5 and 6 and on both sides of a line joining the two locations is an area in wnich extensive shallcw downsic;e mcvement, accarently at the time of the 2", January earthquake, has obscured any f aulting that may be present.
At 1ccation 5 is 0 --' e : f-a:tre tranding .35:4 that snows evidence of right-lateral strike-slip displacement and pecbably is faulting. An alinement array iCalled by P. W. Harsh crosses this fracture.
Fartner south at location 7 are two subparallel northaest-trending fractures seme 2 to 8 m apart.
The western ene shows mostly dcwnniil extension witn possibly a rignt-lateral ecmponent, but the eastern one exhibits ccmpression, the downhill side being thrust over the uphill side, and has a suggestion of a lef t-lateral component. The origin of these two fractures is not clear, but the western one joins a landslide to the south.
From location 8 a series of fractures can be traced intermittently to location 12 on Vasco Road.
Evidence of right-lateral displacement, ranging up to about 25 rm, was found at several places along this portion of the f ault
- ene.
Possibly the fracture zcne between locaticns 8 and 12 extends much f arther to the northwest across the area of landslides to ccnnect with the fractures near locaticn 1.
No surface faulting was found fer 1.4 km southeast of location 12 along the line of the main break, but a series cf hairline fractures trending northeast are visible in the pavement at location 13. Most of these fractures are about on the projection of the main break and a fault strand mapped by Herd (1977), and have the proper orientation to be f ault breaks; however, the fractures are also perpendicular to the read, and to the east, where the road runs east-west, the fractures trend ncrth-scuth.
This group of fractures and a hairline crack in a paved f am road are the only suggestions of f aulting that we saw between lccatiens 12 and 14.
Evidence of f aulting was found at location 14, where 10 m: of 6
l rignt-lateral strike-slip was measured, and at location 15, where north-south fractures in soil indicated some rignt-lateral displacement. At locations 16 tnr:.;n 19 rignt-lateral displacements of as much as 15 = (resolved parallel tc ::re' were measured en 29 February.
Between locations 9 and 16 the trend of tne f ault zone is about N.400W., but between locations 17 and 19 the trer.d is about N.lS0W. Whether this indicates a change in the trend of the main f ault or the presence of a branch f ault diverging from the general trend is not clear.
No faulting was seen near Frick Lake on the projection of the N.400W. trend, but an alinement array has shown right-lateral af terslip just east of, but not at, location 19 (P. W. Harsh, personal comunication).
This evidence suggests that the ruptures at locations 13 and 19 are on a branching break and that the main break continued on a more southeasterly trend, along the f ault strand mapped by Herd (1977), probably to location 23 where the right slip on a fracture increased froni about 1 cra on 29 January to about 2 =
29 February and 3 = cn 1 April.
No paved roads exist between Frick Lake and location 23, and f aulting of such small displacement would be extremely difficult to find between those places.
Subsidiary breaks within the Greenville fault zone A zone of faulting, here referred to as the northeast break, extended discontinuo'usly from near location 26 southeastward across Vasco Road to location 31, close to a strand of the Greenville f ault zone mapped by Herd (see pl. 1). The part extending northwest from Vasco Road showed extension perpendicular to its trend and generally scme vertical displacement, with the scuthwest side relatively down-dropped by 20 to 30 crn.
The strike-slip component of displacement at the time of our examination (24 January and 5 February) was both right-and lef t-lateral. This peculiar circumstance is procably the result of right-lateral f aulting of small amounts (20 mm or less) accompanied or followed by local downslope movement of the wet soil as the 7
result of shaking.
In support of this explanation are the f acts that a) the fractures usually are lef t stepping even where lef t-lateral components are present; b) on flat ground (such as location 29 and the northern cart of location 27) the strike-slip component is right-lateral; M c) the continuation of the zone southeast of Vasco Road shows right-lateral components of displacement.
At the white line on the southeast side of Vasco Road (location 29), Wilson and Keefer measured 20 m of right slio, 40 m of extension, and 30 mm of vertical displacement (down on the southwest) about 3:30 p.m. 24 January.
The part of the northeast break that lies southeast of the Vasco Road crossing lef t-steps about 20 m to the east of the part northwest of the road, but has the same general trend.
The fractura in the part southeast of Vasco Road generally show extension and little or no vertical compenent, and in many places have evidence of a right-lateral slip component and a lef t-stepping pattern. The greatest extension and right-lateral strike-slip displacement measured on this part of the northeast break were about 25 mm and 13 mm respectively.
The fracture zone in the west half of section 23 (location 32, pl. 1) is here referred to as the southwest break.
It extends at least 0.3 km (access problems prevented complete mapping) over a hill, across a valley and up another hillside.
This fracture, like many of the others, shows mcstly extension, but a right-lateral component (maximum 5 m) was observed at several places.
Other fractures within or near the Greenville fault zone New or newly-widened fractures were seen at various places within or near the Greenville f ault zone; scme cf these are probably directly related to f aulting and others are probably related to ground vibratien.
On Laughlin Road at location 20 a group of more than 20 hairline fractures trend about N.40-600W., diagonal to the road.
Although only extension was seen on these 8
fractures they probably resulted from f aulting because they cross the road diag:nally instead of perpendicularly, they are parallel and adja:ent t: two f aults mapped :y He-d (1977), and they have crcwn with time (only two fractures were cetected on 25 January but mere than 20 coul: be seen :q 29 J an uary).
Locations 19 and 20 possibly are en one splay parallel to the west site Of Frick Lake.
Many fractures cross the north frontage road of Interstate Hi;nway 550 and Greenville Road between locations 21 and 23.
These fractures are perpendicular to the roads, changing trend as the pavement changes direction.
Many cf tnese fractures are obviously old, having been patched or having weeds growing in them before the earthquakes, but some seem to be new.
Near locatien 22 are several conspicu:us open fractures. One fracture on the north-south part of Greenville Road showed extension of 6 mm, ste; ped to the right, but showed no lateral or vertical component and did not break the c:n: rete civider. At location 23 a probably old fracture trending N.400W.
(also perpendicular to road) showed new movement, including right-lateral discla:ement that was about 1 mm on 29 January, but was about 2 mm on 29 February and 3 mm on 1 April. This fracture, whicn is dire:tly on the proje: tion of a strand of the Greenville f ault zone shown by Herd (1977) is the only one between locations 21 and 23 that showed definite lateral displacement, and the displacement may be directly related to f aulting.
The f ault en the projection of which it lies is shown by Herd (see pl.1) as extending northwestward close to locations la through 17, where f aulting occurred this year.
The south frontage road (location 24) and the adja:ent parts cf Greenville Road show nunerous f ractures.
These almost all trend perpendicular to the roads, trending about north-south on the frontage road and about east-west on Greenville Road. One fracture about 150 m west of Greenville Road had weak indications (small differences in width along length) of less than 1 mm of 9
rignt-late al cis: lace ent but none of the others had evidence suggestive of tect:nic 1 iteral displ1:sment.
Cr Vas:: 0.02d at ;t 2 km n:rth f the county line (1 :acien 25) several fra:tures in the pave ent were found by D. K. Keefer and R. C. Wilson on 24 January.
These fra:tures trend about N.700E., are rignt-stepping, and on 5 February had as much as 2 nTn of lef t-lateral and 3 m of vertical displacement on them. The fractures are visible only in the pavement and for a shcrt distance onto one shoulder of the road.
The roadbed is probably on bedrock but a thin fill could underlie at least part of the pavement.
The origin of these fractures is not clear.
They are not readily explained by downslope movements.
If they are the result of f aulting, it must be very local.
Two cracks across Morgan Territcry Road (near S. line of sec. 5, T. 2 5.,
R. 2 E., 3.4 km northwest of location 1 and beyond the limits of pl.1) were observed by Brabb en 25 January.
The cracks trended N.35CW. and had about 2 m of right-lataral displacecent.
They are en the extensien of the Greenville f ault as shown by 3rabb and others (1971) and could represent tect',nic dis;11:ement, but they could also be related to settlement of the road.
At least 15 other cracks were visible in the pavement of Morgan Territory Road on 1 A:ril within 0.7 km north cf the cracks noted by Brabb. One crack was 0.2 km north of the Marsh Creek f ault as shown by Brabb and others (1971).
It had a trend of N.81oW. (nearly perpendicular to the road) and showed 2 or 3 mm
(
of right-lateral displacement.
At least half of the road is on fill at that I
point.
This crack, like the others in this area, is probably not the result of faulting.
l i
Breaks witnin the Las positas f ault zone The Las Positas f ault zone, rec 0gnized and mapped by D. G. Herd (1975, 1977), strikes northeast along the southeastern margin of Livermere Valley.
Fractures were observed at. locations 33, 34, 35, and 35 along Mines Road, Tesla Road, Las Positas (Vasco Road) and Greenville Road where mapped traces na
of the las Positas fault intersect paved roads.
Plate i and figure 1 show tnese 4 localities in relation to the mapped fault traces. On 7 February these localities were inspected and the fractures were described and mapped (figures 2, 3, 4, and 5). On 29 February the localities were revisited and inspected for new fractures or modifications to earlier fractures.
At Mines Road (location 33) eight sets of fractures designated 33A-33H were observed on 7 February as sketched in figure 2.
The fractures are located 210 to 250 m south of the centerline of Tesla Road. A:imutns of segments of the fractures range from 760 to 1090 but trend approximately perpendicular to Mines Road; the fractures are largely confined to the northbound lane. Only 33A was noted to extend across the centerline on 7 February.
Prior to 7 February, other investigatcrs used orange spray paint to mark fractures 33A, 333 and 33C; fractures 330-33H had not been painted. On 7 February, no measurable vertical or lateral displacements were associated with the fractures 33A-33H.
No apparent post-paint propagation or extension of fractures 33A-C was observed.
On 29 February location 33 was reinspected.
Blue paint had been applied to fractures 330-33H. Fracture 33G now crossed the centerline of Mines Road, but had not grown since application of the blue paint.
No displacements or apparent propagation of fractures other than 33G was observed.
The fractures at Mines Road (location 33) exhibited dusty, weathered surf aces and did not expose freshly broken, black asphalt as did other fractures caused by tectonic displacement or by non-tectonic ground f ailure.
Although fractures 33A-33C apparently coincide most closely with the trace of the Las Positas f ault (Herd,1977; figures 1, 2, this recort), the absence of measurable displacement and the rather aged appearance of ne fractures and their geometry (perpendicular to Mines Road) suggests a non-tectonic crigin.
The extension of fracture 33G across the centerline of Mines Road observed on 29 February followed a period of heavy rain.
The extension of this feature, 11
if tectonic in origin, is the a::arent south estern limit of effects related to probable surf ace rupture en the las P sitas f ault.
(inspected 7 r :rua y) nine fract;ra:
At locati:a 3a a':r; Tesla.:a:
e c:::-ise three rignt-ste::ing en echelon sets of fractures (sketched in figure 3).
Fra:: ares 3;A, 345, ar.d 34F-34I coincide with mapped traces or lie on the
- ::e::icns cf ma::et tr2:ss of tne Las Positas f ault zone (figures 1 and 3).
ra:ture 22: displays a::ut 1.5 cc: lef t-lateral strike slip displacement.
P:st-eartng;ake propagation of fractures C, 5, and F apparently occurred; the cracks extended through and beyond spots of blue spray paint which reportedly marke: the ends cf the cracks at the time the paint was applied.
Surfaces of ali fractures at location 34 exposed fresh, black asphalt. Ccroonly, pebbles had been "pcpoed" from their positien adjacent to the fracture edge.
The observed lef t-lateral strike-slip displacements, the right-stepping en schelon distribution of fractures associated with maoped traces of the las
- sitas f ault, the un:ues-icned recency of the fra:tures and their grow *.h or 3:03asien f:llcwing the earthquakes of 24 and 25 January indicate that the f ra:tures on Tesla Road are probably tectonic in origin.
At location 35, examined 7 and 29 February, five fresh fractures were ma;:ed (figure 4) near the Las Positas f ault intersection at Vasco Road (called "Las Positas Ave" on pl.1 and fig.1). Positions of tractures were measured, using a tape, north from the centerline of Tesla Road.
Fracture 35E, a prominent break near the crest of the scarp of the Las Positas f ault, exhibited lef t-lateral strike slip displacement of about 0.5 nn.
Fractures 35 A-D did not exhibit dis:lacements.
Fractures 35A-35C occurred only in the scuth:cund lane; only 353 extended across the center line of Vasco Road.
Fractures 35A-350 trend generally perpendicular to Vasco Road, and have merely opened with slip vectors criented downslope and perpendicullr to fracture trend; these features are interpreted as non-tectonic grouno f ailure.
w
The small amount of left-lateral strike-slip measured at 35E coincident witn the trace of the Las Positas fault indicates that surface ru ture on the Las ?:sitas f ault extended at least 1.1 km f-: Tesla :. cad to Vas:: R:ad.
T'.is interpretatica is strcngly supported by data frc an alinement array unich showed about 6 m of lef t-lateral displacement across the fractures at location 35 between 21 February and 26 March (P. W. Harsh, personal coc unication), even though fracture 35E showed no obvious change between 7 February and 1 April 1980.
At location 36, near where the Las Positas fault zone intersects Greenville Road (figure 1), four fresh fractures without measurable lateral displacement were noted.
Three fractures trend perpendicular to Greenville Road and one is diagonal to it.
As mapped on 7 February these features are shown relative to the northeast abutment of the Greenville Road bridge where it crosses the South Bay aqueduct (figure 5).
No extension or growth of fractures was observed on 29 February.
The orientaticn perpendicular to Greenville Road and the absence of growth or a history of propagation indicate a probably non-tect:nic origin for these fractures.
The explanation that best accounts for all observations, including the left-lateral displacements, the right-step:ing en schelon fracture patterns at Tesla Road, the continued propagation of fractures after the earthquake, the alinement array data, and the spatial association of all observations with the mapped traces or scarps of the Las Positas f ault zone, is that left-lateral tectonic displacement occurred on the las P sitas fault zone during and after the earthquakes of January,1950.
Relation of the January 1980 f aultino and fracturine to oreviousiv marted f aults As shown on plate 1 the main break between locations 1 and 17 lies very close to a f ault strand in the Greenville fault :ene mapped by Herd (1977, and 13
l unpublished data). As discussed previously, a possible extension of the main trace southeastaard fecm location 17 to location 23 would closely follow the i
f ault strand shown by Herd (1977).
The northwest break was within about 25 m of a f ault strand mapped by Herd (unpublished data); see plate 1.
The soutnwest break was 80 to 100 m from a strand mapped by Herd (1977).
The diagonal northwest-trending fractures on Laughlin Road at location 20 are parallel to and within about 100 m of two f aults shown by Herd (1977).
The fractures at localities 33 through 36 are nearly coincident with strands of the Las Positas fault zone as shown by Herd (1977).
Evidence at locations 34 and 35 indicates lef t-lateral tectonic displacement in the fault zone in 1950.
Herd (1975,1977) had previously inferred lef t-lateral oblique slip on the Las Positas f ault zone.
3ultino and fracturina to the earthouakes R el ati r
^#
The.cr:rernmost surf ace f aulting is about 9 km southeast of the epicenter of the 21 January earthquake, but an eyewitness account (San Francisco Chronicle, 25 January 1980, p. 3) at the time of the earthquake and field observations by Harsh, Wilson, and Keefer the af ternoon of 24 January shcw that the breaks across Vasco Road (locations 12 and 29, pl.1) were associated with the 24 January event.
Faulting associated with this event or its af tershocks evidently extended at least to Laughlin Road 0.4 km northwest of Frick Lake (location 16), where a few lef t-stepping en echelon fractures having a N-S orientation were observed by 3rabb on 25 January. Other fractures were observed by Brabb on the same date along Laughlin Road (location 18), 0.4 km south of Frick Lake (location 20), and along the frontage road of Interstate Highway 580 near locations 22 and 23.
Following the 26 January earthquake the number of fractures northwest of Frick Lake was found to have increased, as was tne number of fractures on Laughlin 14
Road at location 20.
At the latter place Brabb found only two fractures on 25 January, but by 23 January m:re than 20 fractures were visi:le.
The amcunt of right slip at location 23 in:reased in Fe:rua y and Ma-ch.
~
Ine timing Of :ne # a:: ring i n the Las ?:si:as #ad: ::ne i: n:: well known. We first saw the frae: ares on Tesla R ad anc Vasco Road on 1 February. As described ab:/e, s:me gros:5 of the fra::ures :::urred at locations 33 and 34 between ~ and 23 Fe:ruary, and the alinsnert array data indicates lef t-lateral displacement was continuing bet een late February and late March at location 35.
Other individuals and organizations have m:re data en the changes in numcer, length, and displacement on the various fractures (some data of this kind is given by Secr:ssian and others,1930) and the reader is referred to their future reo:rts.
SUMERY The surf ace f aulting ass: iitad wit, the earthquakes on 24 and 25 January 1330 was confined to the area m:re than 3 km southeast of the 24 January epicenter.
The surf ace f aulting was discontinuous, had snall displacements, and in places was difficult to se:arate from downslope gravity movements that accompanied the earthquakes. The main break within the Greenville f ault zone had a trend of about N.380W., could be recognized at several locations over a distance of 4.2 km and may have extended as f ar as the vicinity of Interstate Hignway 530, givinc a possible length of 6.2 km; 5::5 of these lengths include more gaos than served' surf ace ruotures. AI:ng 0.5 km of its length near the northwest end the main break may have consisted of two subparallel traces about 30 m acart, but extensive s10:e f ailures in that area did not permit a definite interpretation regarding tnat point. Maxicum l
displacenents measured by us were a::ut 25 mm of rignt slio on 23 January; i
r 15
O vertical coco 0nents cf as mucn as 50 mm were seen locally, but these were difficult to se:arate frc? gravity effects.
The main 1953 break was very c? css : a f aul: *' thin tne 3 aenv'lle f ault zor.e ra::ec :/ Herd (~.977, and unpub'.ished data).
Tne northeast break (locations 26-31) within the Greenville fault zone could be fclicwed f or about 0.5 km, and lay 0.12 km to about 0.25 km east of the main break.
The part northwest of its intersection with Vasco Road has a general trend of about N.460W., and the part southeast of the road crossing, which lef t-steps about 20 m to tne east, has a general trend of about N.440W.
Both parts were characterized by extension (as much as 40 mm) and, in many places, a right-lateral strike slip component (as much as 20 mm).
The northwestern part generally had a vertical cocoonent, relatively down on the southwest side; part of the vertical component may result from downslope gravity movement wnich is believed to account for local areas of lef t-lateral disolacement found on this part of tne break.
The northeast break was very close to a f ault strand ma;oed by Herd (unpublished data).
The southwest break (location 32) is at least 0.3 km long.
It lay 0.25-0.3 km southwest of the orojection of the main break and trended about N.330W.
This fracture shc a: ::stly extension, but a ri;nt-lateral component (as much as 5 mm) was seen at several places.
This break was within 100 m of a strand of the Greenville f ault zone mapped by Herd (1977).
Extensional fractures on the frontage roads north and south of Interstate 530 and on adjacent parts of Greenville Road do not seem to be related to f aulting of the usual kind, but may be related to regional extension or other processes.
An exception to this generalization is the fracture at location 23 which showed progressive increase in right-lateral displacement over time and is directly on the prcjection of a f ault in the Greenville f ault zone mapped by Herd (1977).
m
A group of more than twenty fractures, most less than 1 mm wide, are visible in the paver.ent of Laughlin Road at location 20.
They are diagonal to tne road, are parallel and adjacent to tw0 previously macced f aults, and most of them developed between 25 and 29 January.
Their orientation, locatien, and growth suggest that they are related to small tectonic displacements on mapped and unmapoed f aults in the Greenville f ault zone.
The snall lef t-iateral displacements observed at locations 34 and 35 and the rignt-stepping fracture sets and propagating fractures observed at location 34 indicate that small tectonic surf ace displacements, as well as n0n-tect nic ground f ailure, cc:urred along the Las Positas f ault zone during and procaoly af ter the earchqua<es of January 24-27, 1930.
Data from an alinement array at location 35 indicates about 6 mm of left-lateral displacanent between late February and late March 1980.
Concurrent surface displacement en two f aults having a conjugate relation to one another, such as between the Greenville and Las p:sitas f aults, has occurred before.
Examples are t"e f aulting ass:ciated with the Tan;2, Ja:an, earthquake of 1927 (Yamasaki and Tada,1923) and the 'i rth I:u, Ja;an, earthquake of 1930 (Matsuda,1972).
1 17 j
REFERE.' ICES CITED Bedrossi an, T.
L., Bezore, S. - P., Sherburne, R. W., and Wootten, T. M.,1980, The Livermore earthquakes of January 1930, C:ntra Ccsta and alameda Counties, California: California Geology, v. 33, nc. a p. 32-92.
Brabb, E. E., Sonneman, H. G., and Swi t:er, J. R., Jr., 197', Pre'iminary geologic map of the Mount Diablo-Byron area, Centra ^: I a, A:ameda, and San Joaquin Counties, California:
U.S. Geological Survey Open-file maa.
Herd, D. G.,1975, The Las Positas f ault--An active, northeast-trending lef t-lateral fault in eastern Alameda County, California:
Geolcgical Society America Abstracts with Programs, v. 7, no. 7, p.1110-1111.
Herd, D. G.,1977, Geologic map of the Las Positas, Greenville, and '/erena f aults, eastern Alameda County, California:
U.S. Geological Survey Open-file Report 77-659, 25 p., map scale 1:24,0C0.
Matsuda, Tokihiko,1972, Surf ace f aults associated with Kita-I:u earthquake of 1930 in Izu Peninsula, Jacan, in Izu Peninsula:
Tokai 'Jniversi ty Press,
Japan, p. 73-93, in Japanese with English summary.
Yamasaki, Maomasa, and Tada, Fumio,1928, The Oku-Tango earthquake of 1927:
Tokyo Univ., Earthquake Research Institute Bulletin, v. 4, p. 159-177.
I 13
Table 1.
Field Observaticns Location Obs ervations 1
Zone 100 m long, trend N.470W.; individual coen fractures in soil trend N.250 - 350W., have lef t-stepping in echelon relation to the zone. At one point, right lateral displacement of 11 mm parallel to zone and extension of 20 mm perpendicular to
- one (1 Feb.).
Local minor lef t-lateral component, probably from downslope gravity movement.
2 Zone trends N.300W., consists of at least 7 fractures in soil, on most of which right lateral separation could be seen.
Site of survey quadrilateral installed by P. W. Harsh.
Zone may extend 40 m f arther NW. where a pair of lef t-stepoing fractures could be folicwed for 15 m; extends at least 20 m to SE.
Includes small graben with maximum depth cf 70 mm.
3 Zone trend N. 3 cow. consists of discontinuous fractures that trend N.?^9-35cW.
A taut rect and match of pebble with its mold provided a calculated right lateral displacements of 18 mm parallel to zone and extension of 47 mm perpendicular to zone.
4 Zone trend N.380W. individual cracks generally show relative uplift (max. 50 mm) of northeast side and as much as 30 mm extension; a " bridge" of sod attached to both walls indicated a right lateral component.
5 Two isolated en echelon left-stepping fractures in dirt road indicate right-lateral displacement but unable to measure r: cunt.
Northeast of a line joining loca:icns 4 and 5 are some short fractures that are probably related to dcwnslope gravity movements, althougn one showed 6 mm of rignt-lateral separation 19
combined with 27 mm of extension.
Between locations 5 and 6 and en both sides of a line joining them is an area of extensive l ands li ding.
5 Prominent fracture in soil, at least 30 m 1:ng; trend N. 35:W.;
strong suggestion of right-lateral component based on differences in crack width and probable match of points across break; relative vertical displacement m:stly down on downhill side but not consistent.
Survey alinement array installed by P. W. Harsh on 25 January crosses this fracture.
7 A pair of fractures, in soil, that intersect an E.-W. fence on the half-secticn line. West fracture trends N.270-320W.
shows mostly dcwnhill extensicn (maximum vertical 90 mm, 5 Feb) but may have a right lateral component.
Extends south of fence where it becomes part of a landslide studies by R. V. Sharp.
A: ut 2.4 m to 9.3 m east is another fracture, somewhat concave upsic:e in plan, with a general trend of abcut N.23:W.
This fra: ure is in c:::ressier with thrusting of d:wnhill side over u;niil side; maximum vertical component 70 mm. The ene place where lateral comp nent could be inferred (5 Feb) indicates left l
lateral, but very uncertain.
The origin of these fractures is
~
not clear.
l l
8 Fracture zone in soil, trend N.270W., consists of left-stepping l
l l
fractures, extends SE. from N-S fence that is on the quarter-l l
secticn line.
Rignt-lateral displacement parallel to zone at two i
l points (23 Jan) ranged from 10 mm to 25 rm.
Farther to NW are i
other fractures with the same trend but they may not be of tectonic origin.
9 Fracture zone in soil, trend N.270-300W., traced 52 m.
Unable to match edges of fracture to measure right-lateral 20
displacement but could be a few centimeters.
13.
Singie fracture in soil, trend N.300W., rign -lateral strike slip 8 mm, calculated parallel to average zone trend of N. aow.
Between locations 10 and 11 the f ault tra:e was visible at several places; although evidence of right-lateral displacement was seen, we could not measure it.
11 Lef t-stepping fractures in soil; measuref 22 mm of right-laterai strike slip 1 February which had increased abouc 1 nT7 when remeasured 6 February. Unable to find f ault traces between localities 11 and 12.
12 At Vasco Road.
Pressure ridges and fractures fermed in the pavement which is built on artificial fill.
At time of our detailed examination (23 January) the pressure ridges had been removed and many of tne edges of the fractures had been modified by truck traffic, but rignt-lateral strike-slip displacement was estimated at about 2 cm parallel to the :one trend of N.300W.
Fault traces were not visible within 0.5 km SE. of Vasco Road.
13 Road to East Alameda County Dump.
S u.c hairline fractures extending perpendicularly across this paved road were visible 31 January; at least 4 cracks were present 25 January. Most of the cracks lie near the projection of the main break, have a NE trend, and may represent incipient f aulting.
14 A short fracture zone, trend N.400., was found in soil at the W
base of a scarp-like rock outcrop.
Individual fractures trend about N.lSoW. Right-lateral strike slip was 8 mm parallel to zone and extension was 4.m perpendicular to zone on 30 January.
15 2cne of fractures in soil; individual fractures trend N-S; probable right-lateral strike-slip.
21
16 Fracture zene trending about N.300W. crosses Laughlin Road; first cbserved oy us on 25 January.
Individual fractures trend N-5, step to left. Difficult to ccnfidently match points across tse fractures but strike slio parallel to one may be as mucn as 6 mm on a single break (29 February) including af terslip.
Fractures could be traced NW. into cultivated field but we did not see them to the SE. of the pavement.
Between locations 16 and 17 several hairline cracks with no displacement cross the pavement approximately perpendicular to the road.
17 A fracture trending N.190W. showing about 3 mm of right lateral disclacement (measured parallel to crack; 28 Jan) in dirt NE. of pavement.
13 Group of northeast-trending fractures in pavement.
The most conspicuous one trends-N.70E.
Slip vectors measured at two places on this fracture 29 February were 13 mm in N.20cW.
direction and 15 mm in N. 250W. direction.
Resolved parallel to trend of zone (between localities 18 and 19) the rignt lateral strike slip was 14 to 15 mm; right lateral displacement resolved parallel to the fracture ranged from 12 to 13 mm, of which as much as 6 mm occurred af ter a white line was painted across the fracture by Woodward-Clyde consultants en ?5 January. On 29 February extension perpendicular to the fracture was as much as 8 mm, and vertical separation near center of road was as much as 2 mm (down to SE) but was not detectible at edges of road. Only one hairline fracture was observed at this locality on 25 J anuary.
The fracture had widened and moved 2 mm right-laterally i
l by 13 February; many more fractures were present on 13 February 22
than on 25 January, indicating that they were related to the 25 January event or subsequent movement.
l 19 Fra:ture zone in sh:ulder of road cc:ssed icw cut at SW edge of l
right-of-way and extended into field. On 2S January right-lateral displacements were 7 mm resolved parallel to fracture zone and 6 mm resolved parallel to the direction between locations 13 and 19.
Site of alinement c ray installed by P. W.
Harsh 30 January.
23 More than 20 hairline fractures in the pavement of Laughlin Road.
Spacing between fractures (29 January) ranged from 1 m to cu m and trerds ranged from about N.40cW to about N.60CW.,
diagonal to the road. The nenber of fractures increased thru time - only two fracturcs were visible on 25 January.
21 Fractures between locations 21 and 22 crcss frontage road N. of Interstate 553 per;en:tcularly.
Sc e, pe-ha:s all, are old fractures in the pavement that a;:arencly opened wider during the eart hquakes.
22
.ntersection of Greenville R:ad and frontage road.
Several fractures, some old (possibly associated with previous seismic events) and some apparently new.
Nearly all confined to asphalt pavement and not breaking concrete curbs; orientation about N-S.
One conspicuous crack on N-S cart of Greenville Road showed (29 January) extension of 6 mm, no lateral displacement, did not break the concrete divider and died out to south within 11 m.
23 Between locations 22 and 23 are at least 17 fractures, most if not all old, but with additional extension presumably at the time of the earthquakes.
Spacing between fractures ranges from about 3 to 73 m with concentrations of fractures in certain areas.
The es
fractures show only extension except for one at location 23; tnere a fracture trending about N.400h'. sho ed about I m of right-lateral displacement (29 January) and 2 m of extension.
The right lateral component had increased to about 2 mm on 29 February and to 3 m on 1 April. The fracture was best developed in the north part of the road.
It did not reach the south edge of the pavement on 29 January, but did by 1 April.
It could not be seen in the dirt north or south of the pavement. This location is directly on the projecton of a f ault shown by Herd (1977) within the Greenville fault zone.
24 South frontage road of I-530, west of Greenville Road.
Examined in reconnaissance f ashicn 29 February. At least 21 fractures, perpendicular to the road, show only extension except fer one about 160 m west of the centeriine of Greenville Road which had a suggestion of less than 1 m of right lateral displacement.
Close to Greenville Road are several fractures most if not all of which are old; apparent right lateral displacement (1 m or less) on two of them seems to be the result of vertical movement of the inclined f ace of the concrete curb.
Fractures on Greenville Road are mostly perpendicular to that road and at right angles to the fractures on the frontage road.
25 On Vasco Road about 2 km north of the County line.
Several right-steoping fractures in the pavement. One zone trends about N.70cE., crosses entire pavement and showed 1 to 2 m of lef t lateral and up to 3 m vertical displacement (side up not consistent) on 6 February; a subparallel zone a few meters away shows only extension (maximum 5 m), doesn't reach northeast side 24
of pavement but visible in dirt on southwest side of pavement.
Unable to find fra::Jres bey:nd shoulder cf road. Roadbed probably on bedrock (san:: stone and shale di;cing 300 5.50cW,)
but thin fill could be under cave ent.
25 Fracture zone in soil, trend N.330W., could be traced about 30 m by very careful search, including pulling of grass.
Zone at least 5 m wide, consists of three or more fractures up to 5 r.m wice, aoout parallel to :ene.
Except for a left-stepping pattern in places, no evidence of lateral movement was found.
Other f-actures to the east, on a northeast-f acing slope probably result from downslepe n:vement of the soil.
27 Fracture zone in soil, trend N.55cN., was traced 43 m.
It c:nsists of prcminent discontinuous lef t-stepping fractures.
Near south end, differences in widths of fracture indicate a lef t-lateral c: panent, but 15 m to the northwest had 15 m of ri;nt-lateral strike slip measured parallel to trend of zone; s uthwest side generally downdropped, the vertical comconent being as much as 20 mm locally.
23 Frac;ure zone in soil, trend N.450W., traced about 45 m.
Near middle of :ene, lef t-lateral strike slip 10 + 5 m, extension about 30 m, and vertical component (down to SW) about 30 mm.
About half way between locations 22 and 23 is a fracture zene locally trending N.530W. At one point en it both the extension and the vertical c:=;:nent (00,,n on SW) about 20 si and the rignt-la:aral strike-slip compenent was 11 mm and 7 mm resolved pa-alle' to the 10:a1 :ene trend and general zone trend respectively.
25
29 At Vasco Road breaks in the pavement had been repaired at time of our visit ex:ept near centerline of road, where tnere were three princip 1 cracks fermed a zone about 1 m wide, and a vertical c:m:: ent (dean en SW.) was visible.
About 3:30 p.m. on 24 January, just before the repairs were made, R. C. Wilson and D. K. Keefer il:ured and photographed the break at the southeast side of the r: : wnere it was a single fracture.
At the white line there they measured 20 mm of right lateral displacement, 40 mm of extensicn, and 30 mm of vertical displacement, down on southaest.
Because the white line is perpendicular to the f ault, its lateral displace ent represents right slip.
Later visits sh0wed that additional displacements have cracked tne asphalt that was placed 24 January. Thi; fracture zone could be followed continucasly (25 January) as cpen cracks in the soil for at least 100 m northaest of Vasco Road and about 30 m s:utheast..
pbout 40 m n:rthwest from the road en 5 February the fracture shcwed 20
+ 10 m: cf lef t lateral displacement measured parallel to the fracture (locally N.250W.) and some vertical displacement (down on SW, the d:wnhill side).
30 Fracture zone in soil, general trend about N.450W., was traced for 45 m.
At one point right-lateral strike slip parallel to zone was 13 mm and the extension was 24 mm, with no vertical component.
This site is on top of a flat spur with a slight inclinatien to the southeast.
Southeastward from this fracture zone others were found in the next 50 m; these were open, generally had no vertical component and in places showed a left-stepping pattern.
31 Fracture zone in soil, general trend N.450W., could be follcwed 25
for 27 m.
At one point extension was about 25 mm, vertical camponent 27 mm (d:wn to SW), and right-lateral strike slip was 3 mm; downslope movement alone would have given a lef t-lateral camponent.
No other fractures were found to the southeast along the trend of this fault zone.
32 West of Vasco Road in W.1/2 sec. 23, T. 25, R. 2 E.
Fracture trending N.300W. extends discontinuous 1y for at least 0.3 km, extending over a hilltop, across a valley and up another hillside where access problems prevented a further search.
Fracture shows mostly extension but at several places a right-lateral component was found.
The maximum measured rignt-lateral strike slip was 5 m, cambined with 6 mm of extension, both resolved with respect to the map trend of N.33CW.
33 to 35 Described in text, pages 10 to 13.
37 Five cracks trending N.350E. in dirt road and embankments, observed by Brabb on 25 January. Northeast of this location at least 20 cracks trending about N.400E. were visible in the pavement of Vasco Road.
Some cracks step to the right and others step to the left; no lateral or vertical displacement was visible on them on 1 April.
38 Two cracks in Vasco Road, observed by Brabb on 25 January. One crack trends N.760E., and crosses the pavement; the other trends N.810E. and extends across the west lane only.
No lateral or vertical displacement visible on 1 April.
27
- N, p - ~ ~. s- ---.--.-v.,,-.-,-w.
-. - * ~
. ~
- - i
.s 2
s':$
,. 1
.s l_ ; -
U, c'i'.iU
- 0.. \\,.. l'5 2 ' i. 3 M,..
.. / -I./ - (, #2'L s l
.v p /. N y
/o".8 Vy.,
L
,,.s a.
.~
ni.
1%r$
p:}
T'c e
t.I \\_V.V:d<r,\\?::. s wl A
Q i, W J '. a - F 4..
8t
/7 n.. \\,A :.
- \\
3 l '? -
l
,,./ < - J
. - ' /*,' -
.s D
M y' l2 c -
' %'1'
,f\\ l
' uQ E, Ws;,. O g f. r ',
l 5
g E
<<'3
<.,,7- ( J.
' h-) c,..
.(vt.)-
. z"
./ c m-
.w.f%;e.p xs.
......w wd.. W..... g...
o s
g.
DN u c,. e.
4,
/
,r
. '\\
xg g g q,._,g,3
~:
.....--...2....,,
q y*
c 8=
3,,,,1
=
9-
.t ma
}
m o
x E
f h$
,.\\. ~
Q
?
h 5 b,
'\\/ ~,5 c.g 3 f
y;.
3 r..
52
/
\\$
'-'N 5
%* '.. - W A,
ur.p.<4 " M &}I-w=,.?. a...=e C.
a
.? '5 :s
\\.
r-i
\\, o- /
.. -. S,,.
-.4 -
. y..o.
j,*
2 5
,,c _ ( e m
-a as s-r*:
- .; L /
'.t"f.
\\
- 2..
y l
- ..,., I *.
- I- - r...u : s g
,y
. : 'bi us.
m e
.s E..
c-y
., /
, C _ -:- \\.
o
, [-
1 e
l-ch e..
.. s. :
a w (, Q,,
~
.s.,
~.
%... g,1. = @, * ; ;.'
\\n. j..
~3 3"
t
.p\\wg.
'L,..:-,
- Il
- ;. y, 7, 3 - c S, :. ~
=v
~
a 37
/'%o.
\\
.~ q 3
{..
L. N
,1
..j s
-c
=*
.- f.
- 1._ _.,
__s ____ - _ y _.
=.
w Y $ ~%
f i
@m
(_
- {..-
.N u ; \\u.~.
/ ': M.,
/
) W, \\ _ U. 3
{ } ( } - --.,.1.y t
o 1
- g
=*
f/
- 8. ~
u
,, J a, g e r-KQ, -
- C '
- U j
1 c, -
.e. e.
-a
/
- oh F/ 5 Ly ~ -o..
! ". ei
- g-2:
x /.*P"I a\\
. -- n s '<
za y
Nx y o.. g..e..:
1 3
s N2-( N(/.
N
...h.
- l e,\\
j I c:
_s 4 +o-
- e. G..
s:. : e':.
e R
2 e
2 v:.., c.
.t -;
. J,ts s,
> y,g. 7 u
o 18 a-
- n u.
o
,9 e.
smf=j!pfJ i=~
w_ Cf% m
~
r m.
t
. g g 4 g. f,,,
oe g..;.,.:......
3.-
..,. p. f...,:,,& f. W X N /k $
?i i'
E
~
\\.g f.1
'q$-
, e,.
I y.y a
- e..
- u,,:
c.-
-a
=
u.=
. < u.,
i 1.
- g c:w.g N.
..:1.....u 2.3 g"g
-~~
un
-.x u
2 c.. =, u..,.,,
N s..,g
..s
~
m
\\5
- p. m.e s
v.
. w.
a
- s. \\
n l ~_ e o
=,y
., m,...
.o
-( N -
~.
n.
... -a
.x e
.2 s,,/,,w [$ " -
.J..
t h
..o X\\.\\.-.
\\ m.l.
~
7
' ""'t cr. '.__'
f. l l c l ;
5 c
(- a ; !
'D j i o.
i e.
-..\\
.as.A..'1 d d - -
t
!:,m-6 L
s.: 'A
.-~
\\.,
!/~)
u l
__y-----,
~~s:
3:
C U
.s2 to m -
f/
s y
4.
.mu. e.,.
[s 2 0 0 -.
1
- 5 C" of Les h s.tos I
to.t tone f.
}
i 4
5, (2iim)1.
' r%
~
I I
s (215) 2 -
[ _. J B!'
5
{
220-cI l <\\
e
.3 i
1 e
l ~ ~::=.l 9 5 '
E (227) 0
.j 230 -
(23i) E
- cca A
I (2 35),
Co' q j
l 5
t 2
240 ~
(241) G
[
84'
~
l Figure 2 (247) H N
94*
l 250g l
Figure 2.
Sketch map showing fractures in the pavement of Mines Ecad in relation to the centerline of Tesla Ecad and the acproximate position of the las Positas fault
- cne.
4.+ 4. m
.~-
7 3c5 m 23*.
l 3ct J
opprosacte 297) pcsit on of l
- 295 trCee 9 l
(faqu'e1) g 45 4
- 295 i
i 4
a I
27* h li 1286 E
! 27M"
=
j j
i z}
j 2c'; 1l hs
'-275 c..-
- 2,I S
,C '
f2 5
l E
o e
3 l
- 265 I 5
a 8
l z
8 n' M 11;}c 5
W l
I 254'(
- 2***
?
n.
,253;o n
248)C
&0; 10 ' # #l 247) gp,) 180
- 245 cos esim:te.
- IBc g
position of l73 tro:e A en-176 Figure 3 p.
tesced to SW 44* !: N a
"' i" 'I N 1,77 33'
,,7
'[d 7
I m
a:
-i- - - - ( win e s R d 1 - - - - -
o
- l I
i V
l Figure 3.
Sketch map showing fractures in the cavement of Tesla Road in relation to tne centerline of Mines Road and the acproximate pc3f tions of traces of the las Positas fault zene, designated Trace A and Trace B in Figure 1.
+
1 i
j l
400 m g I
i i
l
- .*= :* f ::* ares (3 s' -: 1.
==.
.g.
+
-; 380 -
(3a0 B - l l G6*
e 7
I (3 74: 0 9-.
8 i
[. 3 73 -
h 7e*
l c;;r:simate u.
E J
D0 si tioft of
.*?! **
1 3 360 i
L:s Positos e
I
-t E
f 2 alt BCorp S
i f
N7N ev 5
I i
f f
m see
+
1 i
~ ~ * -
p g-.
N..
3cc_.
f p h,i.i.,
Figure 4 5
s.
f hs
%, =e..
he.
. n.a. e 75*
1 340,
ff
-~A l
7-l C
u We O>
3' - - - - - - L. _
7est.,,.,. _
s e
Figure 4 Sketch mas showing fractures in cavement of '/ascc Read in relation to the center!iae Of Tesla R:ad and the a?:roximate position of the nor-h-facir: scare of the Las Positas fault.
~
a-J E
2 icj Figure 5 o
- - - - - ( Ea st ed - - - y 1
I 4
M l
-+ft-
'""8
ito m 3 r
93 poshon of l
1.cs Postos 105 g g
. fowat tone 5{t (62) E gie 6o -
(59) D So*
I
$ 55 E k
+p l
a So 3
.o l
=
p goe i
-A s
a 30 '
go. E.
o (29) e e
e 2 5,,
ffg,,-
j i
A J
al I
/
j iS 2
I/ / L I s*
i 1
~
i
.A1 -
2, O'3 I
go. duct Boy l
l 6
l o
Figure 5.
Sketch mao showing fractures in Greenville Road in relation to the South Bay aqueduct and the approximate position of the Las Positas fault zone.
.)
a...
.s,,.,
. cc..-n., mu..,.., e
.a,, n r
1
.r n
2*
' p. p
';->:C ; a
~
i
,3.-
~s-
.,68**
1.I
- -* ?
-i. e s eu.an.
- 7..
i i
s--
. 32 -<
, t --
....,.,....,...,,, m !
++
r
~
o ~.
.. n *
- y
..,.- x.:
s.
u.^u...,,....,...o
- -'"t= ' f. 3 f)! 1 (
4.~.ee we se.n.as',..e.*e
.g..*
- m. s,
,. s.
ep
' -s
., ],.,g*
w. /.....
u,,.
p.
e.~.,,o,.n m
mi.,
+
,e..
. 3.;
.. e -. ;..,..y c.,, ;.
4 c.).,, m,y,ra. o/...,..%.
.s
.r n.
e e,,.,. p,-...' -e
.5, g,
- . 2
- v.
- 1. v n. h. *...:../. n
~...m,)".% w.7'".. #e t.(.'.>W,.
w ' %,,.P.,
-s
't
.e.
=- + ;
. \\
.,-r.
w
. C.
sr. ' 9e 1
V'.A'Y 'd ",/,, i, g p(,g($ / d [ *D ' @ , ' [.,; ,
. ~.
- 7. D
.f' Y
=%
,t Es
. _.... _.. ls
' ?W ' t e
.. ;;w. :D, n:. ?...
.g.-
., e...e w
w s
v c.
"4.*p Q, y... "%.
.g.
D~J "f C,... j..~ a,.
V '
.y j
\\
.,4..
,~..,i t u%... =...,.
.. c..
y7
.z
~. y, % aru. s u m.;3 s. w a..a y s
p w.m. _ c..y a_9- -w. yo(.e; g. ~:
.. - - m
-- m, a,.q, - 3.., x,.,Mkp. e.
- _
g,.. ( 3.y, j g, 9-_..4.m, I
, w
~.
s e
er m
y$,
, L. ; i....
g
.Y 8
p' 9-
. L. r. _,.,m.Wa 4,, - '<<e m 1 - ISOy.F S.p,f,b.
~~
i ~
. l....v,.,. -
i
.,,.~-
3
. ~#
.%.. \\.
i e..
t - -
v _.w.xs
,i
~
.s. ~ y y,_
w s
-s,. } s. \\,,
- Y
--- a.1
. e.o
.s a
- -- ",w,,*
z
. %.1
. a..
< v s m. t.. + cm.as ;
wsc n
,a
=,.
s n.
s.
,w
.a
-,...i j
e
.t y~.e..
.... /.
q _4 ;.,, m -- '
.c,
-,}9 g
' fy '
z. w ;. Q. w.m
,'y
.y 1
,a
/-
_ x x.39)4
> 3,;,
,w.
w-
' c., y q. e -9.d, c -
g.
s Am&'
4 gr. g ' *( ' 'f** ~ * ; y.,H v
.y,
,,y e
.y
- t.
..,..,w
,,i
- r. f.
i
~ ' ' "*A* k** * "., g~~i e A' 4.% e
- m. 4.*
) ":o e
f.,
F n. S
.8 4 j' m=g *QMd%
\\r y ; %..
N*',
,:. A
- a...
.f
, %. x.
t.
<. 5 4, a v
- -.. s - m.a
.e..
%z:g.,s.
._?. '..
+.
.y.
u..
. -. ~ ~
l. m m.
- ~.
.v.t.....
a,* -.
.. % y n
w M~ s[* 44. i s.
-G anvaar '.
.,'*1, wA
<u.
.,..a........,_ ~_,.
. w.,,7., ;" - g~...3
,3
_,. _ p~a, s,
. -. =,
s
...c.
f, u
m.*
- . i.,..
,' 5
-~~'#'
e g,,. a, -y
,+
.~,
. _.. q:
.m.
3 i
p s.c%#, j :s* m. _..,
j 1,
pt.A*.
.. e,
xDL
. x
~.n =~.r
~
~.v u
.;i r.-
=
- - M M 73 j g.,
A..
./ W s
sa N :. l. h k..'.: 4 '. ;.:.2 R.. h. w f,, %
i 1..c...,.
. ef,,*. r j- (-
t
\\.
g.s b
.s.
'#* *4 '
.o,c p-
, s 9^
sa 88
,.s.
.m =-~
y n
..y,.u
- z.
~,
.n.
.,~.
.~
,..-.~..D."',
~
.. J.,,%
l
- l 1...
..._s..
a \\.,.
.y }
.o
_,,,I i
5.,
4.'
g m
.w.,,,, m
._,.m.,.. :
,o._..
.,.,m-...
w SUR/ ACE FAULTING NEAR LIVERMORE. CALtFORNIA AS SOCI ATED WITH THE JANUARY 1980 EARTHQUAKES
-by VG Samoa. J J L;enhae'eper sad J C. Tinsley
w. r... r y..
c sna e,
DAVID B. SLEMMONS g
CCt.SULT:NG GECLOGIST 2995 GOLDEN V ALLE < 40 AD RENO. NEVADA 895C6 - (7:2) 972-5.577 April 23, 1930 4
1 Dr. Robert E.
Jackson, Chief Geosciences Branch Division Site Safety and Environmental Analysis U.S. Nuclear Regulatory Commission, Mail Step P-314 h'a s hing ton,
D.C.
20555
Dear Dr. Jackson:
1 1
This letter reviews the geolcgic aspects of the report "Probab-
)
ilitj Analysis of Surface Rupture Beneath Peactor Building, General Electric Test Reactor," prepared for General Electric Company by Jack R.
Benjamin & Associates, Inc. (JBA), on March 12, 1930.
My review does not evaluate the basic mathematical or probabilistic basis of the analysis, but focuses on geologic assumptions used in the analysis.
The primary sources for data used in my review are from General Electric Company sponsored reports and letters, various documents and reports from the U.S. Geological Survey and other organiza-tiens and individuals, and memoranda, letters and reports of the U.S.
'uclear Regulatory Commission.
Some of the more significant sources are listed in my letter report of August 3, 1979.
In addition to studying the written record for the General Electric Test Reacter (GETR) site, I have visited the fielf exposures, and personally examine'd mc-" ^,
(%g@rg: mm:,%
- e 4 g
y-
.m
+
w;;h the exception c:, _ r e.
1 4 n c luc e
. o e x a,.. 4.,.e DUPLICATE DOCUMENT
..,., -.s
.o
-.s fissurinc from the Januar.-
Entire document previously entered into system under:
A B
tot ANo 8006blo%Ef
}
o f Pages:
/f 6'
b 0
4 Robert E. Jackson, April 23, 1980 Page 2 l
i i
I
^
The overall data base from the above sources is adequate for i
f general assessment of seismic risk, but does not resolve all i
geologic or probabilistic issues and values.
The main defici-l encies of the J3A report is related to the geometry of the 1
i j
fault rupture planes or potential planes, and the lack of con-I i
i sideration of the three-dimensional form of the GETR foundation, i
1
' hat in addition to the 36 ft radius, the effect of approximately f
21.5 ft depth of foundation must be considered.
My review uses the term " fault" rather than " shear" for the structures that offset modern soils (solum), paleosols, and stratigraphic units.
My personal opinion is that the 3-1,3-2, a
j 3-3, and H trenches exposed faults that are tectonically con-trolled and that the term "f ault" should be used for their designation.
The report " Geologic Investigations Phase II, General Electric Test Reactor Site, Vallecitos, California" prepared for General Electric Company by Earth Sciences Associates (ESA) Feb., 1979, f
1 j
indicates that they provide an analysis that "To be conservative in the assessment of geologic hazards to the GETR, an evaluation r
was made that assumed that the shear features are of tectonic f
origin and thus have a potential for surface fault offset."
The following topics are considered in this report:
Age Dating cf Soils, Paleosols, and Time of Last Displacement, 3
i 2.
Fault Recurrence Intervals and Fault Slip Rate, l
3.
Three-Dimensional Model for Ruptures beneath GETR,
-,,.,e