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Regional Location:
Preliminary Magnitude: Greenwich Mean Date: |
SPOKANE, WASHINGTON
Ml 3.2 (PNSN) 01/07/31 |
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| Seismo-Watch Significant Earthquake Reports- No. 01-026 | ||||||||||
| More Special Earthquake Reports | ||||||||||
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| SPOKANE, WASHINGTON, July 30, 2001 (Seismo-Watch) -- Residents of Spokane, Washington were shaken again this evening when a M3.2 temblor struck at 6:38 p.m. PST. It was centered just a couple miles northwest of town on the Fivemile Prairie, frightening the local population but not causing any damage. (See TopoZone map of the epicenter) It was part of an ongoing sequence that frayed nerves in the easter Washington community for the past two months.
The sequence seems to have started on May 24 and has consisted of more that 40 tremors at the time of this report. (See list by University of Washington) The largest quakes registered M3.9 and M3.4 and occurred 45 minutes apart on June 25 and initiated a robust aftershock sequence that was fairly brisk at first but has tapered off to a few quakes every few days. This recent M3.2 event seems to have rekindled the sequence, producing ten quakes in the past 48 hours. (See a map by PNSN) The most unusual thing about the Spokane swarm is the loud bang or explosion-like sounds that have accompanied the quakes - even the smallest ones. Several very small events not recorded by the seismographs are reported as pops and bangs which are heard across several city blocks. Whereas usually just a few people report a felt tremor, many residents in the effected neighborhoods call and report similar times and effects, varifying the occurrance of the events. The seismograms from the PNSN Spokane station shows just how often the small quakes have occurred. (See link below.) There are unconfirmed reports of the two larger quakes causing items to topple from tables and shelves and in one report, bricks falling from chimneys. Clearly the most significant effect from the quakes has been the explosion-like sounds which have frightened residents and frayed nerves. Little is known about the recent tectonic activity in the Spokane region, however, the action forms a northwest trend that correlates with the Hangmans Creek lineament. (See TopoZone map of the region) Perhaps the best summary of the action thus far has come from Ruth Ludwin, a research scientists, University of Washington, Pacific Northwest Seismic Network (Ruth's summary). Also see the mainstream news reports below.
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