View source for PNO-V-86-046, on 860721,two Seismic Events Occurred in Mammoth Lakes Area.Largest Event Measured 6.2 on Richter Scale & Second Measured 4.4.First Event Not Felt at Diablo Canyon.Second Event Triggered Teratec Recording

{{Adams
| number = ML20207J559
| issue date = 07/21/1986
| title = PNO-V-86-046:on 860721,two Seismic Events Occurred in Mammoth Lakes Area.Largest Event Measured 6.2 on Richter Scale & Second Measured 4.4.First Event Not Felt at Diablo Canyon.Second Event Triggered Teratec Recording
| author name = Mendonca M, Miller L
| author affiliation = NRC OFFICE OF INSPECTION &amp; ENFORCEMENT (IE REGION V)
| addressee name = 
| addressee affiliation = 
| docket = 05000000, 05000275, 05000312, 05000323
| license number = 
| contact person = 
| document report number = PNO-V-86-046, PNO-V-86-46, NUDOCS 8607290165
| document type = PRELIMINARY NOTIFICATION OF EVENT OR OCCURRENCE (PNO,, TEXT-INSPECTION &amp; AUDIT &amp; I&amp;E CIRCULARS
| page count = 1
}}
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PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-V-86-46          Date 07/21/86 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information presented is as initially received without verification er evaluation and is basically all that is known by Region V staff on this date.
FACILITY: PACIFIC CAS & ELECTRIC COMPANY                          Emergency Classification DIABLO CANYON UNITS 1 & 2                               Notification of Unusual Event DOCKET NOS. 50-275/323                                  Alert Site Area Emergency SACRAMENTO MUNICIPAL UTILITY DISTRICT                    General Emergency RANCHO SECO                                           XX Not Applicable DOCKET NO. 50-312

==SUBJECT:==
SEISMIC EVENTS IN MAMMOTH LAKES AREA As a part of a series of seismic events that began 7/20/86, two seismic events occurred on 7/21/86 in the Mammoth lakes area. The location was east of Lake Crowley and about 15 miles northwest of Bishop, California (37.5' N and ll8.4'W).        The largest event occurred at 0508 PDT on 7/21/86 and measured 6.2; the second occurred at 0744 PDT measuring 4.4 magnitude. The location was greater than 50 miles from any nuclear power plant.
The first event was not felt at Diablo Canyon; however, the second, smaller event did trigger the very sensitive nontechnical specification Terater, recording instrumentation.
The technical specification required recorders did not trigger. The licensee is analyzing
    'the data.
Naither event was felt in the Rancho Seco Control Room and recording instrumentation did not trigger.
Diablo Canyon Unit 1 is currently at 72% power and Unit 2 is at 100%. Rancho Seco is in cold shutdown.
This information is current as of 1000 PDT, July 21, 1986.
CONTACT:     M. Mendonca, RV                      L. Miller, Jr.
FTS 463-3720                         FTS 463-8369 DISTRIBUTION H-St.      /I 2 7      MNBB /NPhillips lW E/W /'2fWillste/ % Air Rights / 2cf Mail:
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