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Weekly Earthquake Reports
Earthquake Alert Bulletin No: 97-172

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):


5.4 Ms

5.9 (NEIC)

14 km

An earthquake registering a preliminary magnitude of Mw 5.9 occurred at 20:13, July 7, off the north coast Honduras in the Caribbean Sea.The quake was centered in the Gulf of Honduras about 30 miles north of Puerto Cortes, Honduras, and 35 miles east-southeast of Monkey River, Belize. Interestingly, there have been no reports from the region regarding the temblor. The quake occurred along the Swan Fractures Zone ­ the boundary between the North American and Caribbean tectonic plate. Numerous strike-slip faults make up this broad transfer zone which extends from the Cayman Islands through the Gulf of Honduras and into central Costa Rica. This was the strongest quake along the Swan Fracture Zone since a M5.4 slightly east of in July 1990. Scientists are quite concerned about the western portion of the prominent fault zone where it come on shore at the Gulf of Honduras and extends into Costa Rico. The eastern portion in the Caribbean Sea has rupture twice with M7's (1910, M7.1; 1976, M7.5) and a couple of M6's (1977, M6.1; 1980, M6.7) but no quake registering stronger than M5.7 has occurred along the western segment since the turn of the century.

This report was delayed due to some computer malfunctions at Seismo-Watch.

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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