ML091530483

E-mail from Andrew Murphy Recent Paper on Seismicity Near the Ramapo Fault

ML091530483
Person / Time
Site:	Indian Point
Issue date:	08/22/2008
From:	Murphy A NRC/RES/DE
To:	Scott Burnell, Diane Screnci, Neil Sheehan Office of Public Affairs, Office of Public Affairs Region I
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Download: ML091530483 (2)

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From: Andrew Murphy Sent: Friday, August 22, 2008 14:34 To: Scott Burnell; Diane Screnci; Neil Sheehan Cc: Stuart Richards; Rosemary Hogan; Jennifer Uhle; Jon Ake; Annie Kammerer

Subject:

Recent Paper on Seismicity near the Ramapo Fault

Scott, To recap our telephone conversation, I have read the recent paper titled, "Observations and Tectonic Setting of Historic and Instrumentally Located Earthquakes in the Greater New York City-Philadelphia Area", by Lynn Sykes and others and published in the Bulletin of the Seismological Society of America, Vol 98, no. 4, August 2008. In addition to publishing a seismicity map of the area covering the time period from 1677 to 2006, the paper identifies for the first time a boundary in seismicity, with earthquakes with magnitudes less than 3 occurring south of the boundary but not north of it. The boundary intersects the Ramapo Fault on the northwest near Peekskill, NY, and this point appears to coincide with an offset in the Hudson River. The southeast terminus of the boundary is near Stamford, CT, with a length of about 30 miles (50 km). The authors inferred that the boundary is a fault.

If the boundary is a fault, it is only about 30 miles long and much shorter than the Ramapo Fault, which has already been considered in the seismic hazard of the area and in the seismic design of the Indian Point NPPs. The Ramapo Fault was already considered in a probabilistic seismic hazard assessment (PSHA) covering the Indian Point area. The newly identified boundary/fault would not change the maximum magnitude in the PSHA calculations; the Ramapo already controls that. The vast majority of earthquakes identified in the paper, the general seismicity of the area, were known and were used in the US Geological Survey PSHA.

Thus, the rate of seismicity used in their PSHA is little changed by the paper. Thus, with the maximum magnitude and the rate of seismicity little changed or unchanged by the paper, the PSHA assessment is not expected to have changed.

This means that the paper would have little overall influence on the perceived hazard near Buchanan, NY. Further, this means that the paper would have little influence of the resolution of GI-199.

Dr. Andrew J. Murphy Senior Technical Advisor for Earth Sciences Division of Engineering Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington, DC 20555 E-mail Properties Mail Envelope Properties (3E54A9B051CAB64F8DA8BE1178BC8D376BF70F6865)

Subject:

Recent Paper on Seismicity near the Ramapo Fault Sent Date: 22-Aug-08 14:34:29 Received Date: 22-Aug-08 14:34:29

From: Andrew Murphy Created By: Andrew.Murphy@nrc.gov Recipients:

Scott.Burnell@nrc.gov (Scott Burnell)

Tracking Status: None Diane.Screnci@nrc.gov (Diane Screnci)

Tracking Status: None Neil.Sheehan@nrc.gov (Neil Sheehan)

Tracking Status: None Stuart.Richards@nrc.gov (Stuart Richards)

Tracking Status: None Rosemary.Hogan@nrc.gov (Rosemary Hogan)

Tracking Status: None Jennifer.Uhle@nrc.gov (Jennifer Uhle)

Tracking Status: None Jon.Ake@nrc.gov (Jon Ake)

Tracking Status: None Annie.Kammerer@nrc.gov (Annie Kammerer)

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