Calculation of the Local Magnitude for Earthquakes Recorded from the Texas Seismological Network (TexNet)
Dr. Florentia Kavoura
Post-doctoral Research Fellow
Texas Seismological Center (TexNet)
Bureau of Economic Geology
The University of Texas at Austin
This presentation is going to focus on the determination of the local magnitude (ML) relation for the earthquakes recorded from the Texas Seismological Network (TexNet). Using a comprehensive groundmotion data set from earthquakes in Texas, this study proposes a distance correction term –log A0, which is consistent with the original definition of the Richter magnitude. The proposed distance correction calculation for the TexNet events accounts for the attenuation characteristics of the direct and refracted waves over different distance ranges. Regression analysis of Wood–Anderson (WA) amplitudes results in a trilinear function, which represents the attenuation attributes of the events under investigation. In parallel, to better understand the attenuation attributes in different areas in Texas, this study investigates the distance correction terms and attenuation characteristics for four different areas which are well recorded: Delaware Basin, Snyder, Fort Worth Basin and Eagle Ford operating area. The derived distance correction relationship results in an accurate ML relationship for Texas that is unbiased over a 200 km distance range.