OKLAHOMA GEOLOGICAL SURVREY, UNIV. OKLAHOMA COLLEGE OF EARTH AND ENERGY
24 HR SEISMOGRAM OF EAST-WEST EARTH VELOCITY AT STATION OKCFA IN SOUTHERN OKLAHOMA CITY


Updated each hour. Note that all times are GMT.



OKLAHOMA GEOLOGICAL SURVEY OKCFA HHE 200 sample/sec 24 hour seismogram

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This is a 24 hour seismogram of East-West earth velocity in Southern Oklahoma City, seismograph station OKCFA. The East-West component of the seismometer is digitized 200 times per second, and the digits are transmitted by internet to the Oklahoma Geological Survey Observatory near Leonard Oklahoma. At Leonard, the 200 samples per second are read into computer memory (RAM) and written on disk. Each five minutes the seismogram is printed on a monitor at Leonard. Each hour a copy of the seismogram is transmitted to the webserver. The times on the seismogram are all Greenwich Mean Time, abbreviated GMT. Subtract five hours from GMT to obtain Central Daylight Time (CDT). Subtract six hours from GMT to obtain Central Standard Time (CST). The short red line shows where 24 hour old data is being written over by data which was current at the time the plot was captured. Seemingly random slow undulations are caused by wind slowly rocking the ground. Organized vibrations, lasting minutes, are waves from distant earthquakes (called "teleseisms"). Short spikes (a fraction of a minute) are very small earthquakes in or near Oklahoma County. Their magnitude is usually in the range of -0.2 to 1.5. The Richter scale and other earthquake magnitude scales do have negative magnitudes for very small earthquakes. See example seismogram below.

This plot was made by Jim Lawson and Amie Gibson using the free Linux operating system, rnning on a PII 350 MHz computer. Murray McGowan, Mike Smart and others at the Guralp factory in Reading UK wrote the plotting software (Murray) and digitizer software (Mike).

The seismometer is a Guralp CMG-3ESPC three component force feedback with corners at 120 sec ( 0.00833 Hz), and 0.02 sec ( 50 Hz). The digitizer is a Guralp DM24NET. Timing is by GPS. The seismometer is in a one meter deep pit in alluvium.