Mexico

Central Mexico Earthquake 06/15/1999 20:42:06.0 UT

During the afternoon of Tuesday, June the 15th, 1999, a devastating earthquake occurred in Central Mexico which measured Mw 6.7 and caused severe damage and deaths. The photo below is a recording made with seismic equipment owned and operated by Charlie Thompson, who is a PSN Network member. His station is located 1296 Km distant from the event.

Another PSN Network member, Arie Verveer, from Australia recorded the same earthquake. His recording of the detection is shown below. The distance from his site
to the seismic disturbance was 16340 kilometers. Both graphs indicate a very abrupt
earth movement.

The next photo shows a spectrum analysis of the time frame which was recorded by
the Elfrad Group beginning approximately one hour before the quake and continuing until about an hour after the event.

Please note the high amplitude of the signal bandwidth from 2.23 to 3 hertz. Also there is increased activity from .02 to .1 hertz. The next graph below was recorded by Elfrad sensors at the Amity Hill, NC site and shows the result after filtering with a pass band of 2.23 to 3 hertz.

The "P" indicator points to the start of the high amplitude bandpass component.
The "S" indicator points to the time of the actual earthquake event. The period of time from the beginning of detection until the start of the quake was 36 minutes and 34 seconds. This detection method uses equipment which records electromagnetic signals which pass through the earth rather than the atmosphere. Seismic detectors record the mechanical vibrations of the earth movement. A third method of detection is with the use of magnetometers which record the changes of magnetic flux surrounding the earth.

The next photo shows a recording of this same earthquake and the changes it produced on a fluxgate magnetometer. This was recorded by Frank Condon of Geo-Seismic-Labs.

Click on Pic to enlarge

The next chart was also produced by Frank and indicates magnetic anomalies during this time period. There has also been some discussion concerning the possibility of the magnetic shift causing the earthquake and vice-versa. There was also a solar disturbance during this span.

Click on Pic to enlarge

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