![]() ![]() We also tried to incorporate an independent variable to characterize the local soil conditions of the recording stations. We found that by using the original distance definition R, (dependent on the hypocentral distance and on the magnitude altogether), the results are basically the same as when using the hypocentral distance directly. For PGV σAandσE are 0.18 and 0.004, while for PGA σA and σE are 0.25 and 0.30, respectively. σA and σE correspond to the intra-event and inter-event standard deviations. Where MW is the moment magnitude, R the hypocentral distance, and H the focal depth (both in km). For comparison and as a selection criteria, we used the decaying trend of the models, the ratio between the observed and the predicted data (logarithmic) as a function of the distance and its standard deviation, and we determined the following attenuation relations: logPGV=−4.36+0.8Mw−0.00015R−0.97logR−0.0041H+σA+σE logPGA=0.31+0.23Mw+0.0011R−1.48logR−0.0022H+σA+σE We tested four models derived from a parametrical form previously proposed for intraplate earthquakes in Central Mexico but using regional data recorded by the Mexican National Seismological Service (Servicio Sismológico Nacional de Mexico, SSN). We present attenuation relations for peak ground velocity (PGV) and acceleration (PGA) for northeastern Mexico, where seismic activity has been underestimated over the years.
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