Seismo-Watch
    Earthquake Alert Bulletin No:     98-235
    Preliminary data indicates a significant earthquake has occurred:

Regional Location:

Preliminary Magnitude:

Moment Magnitude:

Greenwich Mean Date:
Greenwich Mean Time:
Latitude:
Longitude:
Focal Depth (km):
Analysis Quality:

 OHIO-PENNSYLVANIA BORDER

Lg 5.2 (NEIC)

Mw 4.5 (Harvard)

8/09/125
19:52:52
41.47N
80.48W
5.0 km (Fixed)
A
Notations:
An earthquake registering a preliminary magnitude of Lg 5.2 (NEIC), Mw 4.5 (Harvard) occurred at 19:52:52 UTC (3:52 p.m. EST), September 25, along the Ohio-Pennsylvania border. The focal point was fixed at a shallow depth of 5 km below the surface. Analysis by Harvard Geophysical Laboratory suggested the quake occurred along a north-northwest-trending fault plane and the motion was thrust with a slight slip dip-slip component. The quake was centered south of Lake Erie and in a relatively low population area. The epicenter was located about 66 miles east of Cleveland, OH, or 73 miles north-northwest of Pittsburgh, PA, or 15 miles north-northeast of Sharon, PA, near the small town of Greenville, PA, which is close to the Ohio border.

The quake was widely felt in the north-central United States, including Michigan, New York, Pennsylvania, Ohio, and West Virginia, as well as in much of southern Ontario and in part of Quebec, Canada. It was also felt in parts of Kentucky and Indiana. Preliminary reports indicate there was no structural damage or injuries. Light objects were tossed from tables and shelves in the epicenter area and tall buildings swayed throughout the affected area. Some people heard a large roar while others further from the epicenter hear a low rumble.

Pennsylvania activated the State's emergency Operations Center in order to coordinate a local response program. Operators of the nuclear power plants along the coast of Lake Erie reported the quake was not large enough to set off alarms at the facilities and no damage had occurred. There are unconfirmed reports of cracked walls and broken windows in the epicentral. Retail items in stores were thrown from shelves and much glassware and bottles were broken. There was one report of ground settling (liquefaction?). Many people were startled by the shaking which lasted up to 10 seconds, some panicked and got up to run from their buildings when the shaking stopped. Emergency officials in the affected counties have investigators looking for possible damage and more damage reports are expected.

Earthquake activity in eastern Ohio and western Pennsylvania is uncommon. Only one earthquake of similar magnitude has been recorded in historic times (1700-1998). It measured M5.0 and occurred January 31, 1986 and was centered about 20 miles northeast of Cleveland, near Mentor. Most of the damage occurred to houses and commercial structures in Ashtabula, Geauga, Lake, Trumbull, and Wood Counties in Ohio, and Erie County in Pennsylvania. Modified Mercalli intensities of MMI V were recorded over a wide area, with MMIs of VI occurred in areas of soft sediments. Damage consisted of fallen ceiling tiles, cracked chimneys and walls, broken windows and underground pipes. Seventeen people sustained minor injuries. Thirteen aftershocks were detected, including one in the M4 range. Cleveland sustained widespread minor damage. Interestingly, southwestern Ohio did not feel the quake.

Advanced Geologic Exploration has prepared a 16-page report entitled Historical Seismicity of the Ohio Region which includes discussions of the regional seismicity and the seismogenic zones in and around Ohio. There are brief descriptions of historical earthquakes from central and eastern United States as well as from southeastern Canada, and a brief discussion on how Ohio could be effected by unusually large earthquakes, such a those from a repeat of the 1811-1812 New Madrid earthquakes.

Advanced Geologic Exploration has also prepared a similar report for Pennsylvania entitled, Historical Seismicity of Pennsylvania and Surrounding Regions. These are great reference guides for people interested in understand the earthquake risk of these regions.

Each report sells for $25 and if ordered together sell for $40. To order, send check or money order to: Advanced Geologic Exploration, P.O. Box 18012, Reno, NV 89511-8012. Please request reports by name and allow 2-4 weeks for delivery. Purchase Orders available on request for schools or industry.

 
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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.
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