Earthquake Recordings

The following image shows seismograms of the Saint Louis University part of the Cooperative New Madrid Seismic Network - which consists of modern, continuously recording, broadband, digital seismographs. The traces are, from top to bottom in triplets, from stations SLM (Saint Louis, MO), UIUC (Carbondale, IL) , and BLO (Bloomington, IN), which are 391, 502 and 707 km, respectively from the USGS location of

Date	Time (UT)	Latitude	Longitude	Depth (km)	Magnitude	Location
99/05/13	14:18:22	39.10N	94.70W	5.0	3.0Lg	MISSOURI-KANSAS BORDER [MAP]

The traces are for each station are show in triplets, representing the three components of ground motion, radial (up is away from the source), transverse (up here is to the right when looking in the radial direction) and vertical (up is ground moving upward).
Because of the small size of this seismic event, the original signals were bandpass filtered between 0.3 and 2.0 Hz using a 4 pole Butterwork filter, e.g., the sac command,

bp c 0.30 2.0 np 4

From a seismologists point of view, the very interesting feature of this earthquake is not that it occurred near Kansas City, Missouri, but rather the presence of the low frequency surface waves (Rg) seen on all three components of the stations. These waves are shaped by the continuous paleozoic strata between Kansas City and Bloomington, Indiana and are a very strong indication of a shallow earthquake. We can thus rule out the possibility that the earthquake was greater than 15 km deep. A detailed computational study should be able to refine the source depth to within an error of a few kilometers.

Earthquake Reports

Kansas City Star

Updated May 14, 1999

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