Alert Bulletin Archive


Place Your Banner Here! Info?

Weekly Earthquake Reports
Earthquake Alert Bulletin No: 97-177

Preliminary data indicates a significant earthquake has occurred:

Regional Location:

Preliminary Magnitude:

Moment Magnitude (Mw):

Greenwich Mean Date:
Greenwich Mean Time:
Focal Depth (km):
Analysis Quality (A-D):


2.9 MD


7.4 km
The strong earthquake swarm which began at Mammoth Lakes at 7:58 a.m July 7 and has continued throughout the day and as of 8:30 p.m. July 8, has totaled 328 events. 50 earthquakes have registered in the M2 range but none have topped the M3 mark as of yet. The event listed above is one of the two largest quakes detected in the swarm. The rate of activity surged substantially between 10 and 11 a.m. this morning when 42 events per hour were recorded. The activity remained in the 30 events per hour range for another 3 hours then declined to 3-7 events per hour till present. It is unknown how this swarm will continue and pauses in swarm activity are common before releasing another surge in activity. The depth of the activity is fairly consistent, between 5-8 km, and indicates movement near the upper portion of the magma chamber which could be caused by hydrothermal fluid migration, tectonic strain, magma diking, etc.
Subtract 7 hours to obtain PDT or 4 hours for EDT
Location Quality: A (good), B (fair), C (poor), D (bad)
Magnitude: Ml (local or Richter magnitude), Lg (mblg), Md (duration), Mb (body wave), Ms (surface wave), Mw (moment)

Sources Include:
U.S. Geological Survey, National Earthquake Information Center, Golden, CO (NEIC)
Harvard Geophysical Observatory, Harvard University, Cambridge, MA (HRV)
International Data Center, Center for Monitoring Research, Arlington, VA (IDC)
California Institute of Technology, Pasadena, California (Caltech)
various wire reports and/or personal communications

All data are preliminary and subject to change.
Copyright © 1996 Advanced Geologic Exploration
Voice: 702-852-0992 / Fax: 702-852-3226
Web Site:
Re-transmission prohibited. All rights reserved.