SHALLOW SEISMIC REFLECTION AND GPR IMAGES OF THE SOUTHERN END OF IMPERIAL FAULT IN MEXICALI VALLEY, BC, MÉXICO

We present images of sediments from optimum offset shallow Seismic Reflection and GPR profiles surveyed across the southern trace of the Imperial Fault in sites where the fault trace is not visible and where the fault is visible but has vertical component. The Imperial Fault is a remarkably active right-lateral strike-slip fault with 69 km length located within San Andreas tectonic system whose southern end changes the direction of the strike fault and has a vertical component. Although many geophysical studies have been made in the Mexicali Valley they have been focused to geothermal exploration and although studies exist related to the location of the trace of the fault did not exist seismic and GPR images across the fault so much in the area where there is no vertical component as in the area that if there is vertical offset. To image the fault in these sites, we carried out common-offset single-fold GPR profiles using a RAMAC/GPR System at 100 and 200 MHz frequencies. For the seismic reflection imaging we used a 24 data channel Geometrics Strata Visor NZ Seismograph using 100 Hz frequency geophones and a sledgehammer of 3.632 kg as energy source. We carried out optimum offset seismic reflection profiles in the same location where GPR lines were surveyed. The data sets were corrected and processed. The obtained images allow us to observe the behavior of Imperial Fault between 0 and 10 meters in three sites: the first, where there is no vertical component; the second, in the site where there is vertical offset and the third, in the site where the Imperial Fault begins to have vertical displacement.