Determination of the fault plane and rupture size of the 2013 Santa Cruz Earthquake, Bolívia, 5.2Mw, by relative location of the aftershocks

could generate earthquakes up to 8.5 Mw. Nevertheless most of them are shallow and have low magnitude. In 2013, a 5.2Mw earthquake occurred in Santa Cruz de la Sierra. The five largest aftershocks were registered by the International Seismological Centre (ISC) and 33 smaller aftershocks were recorded by the Observatorio San Calixto (OSC) in the two months after the mainshock. Distances between epicenters of the aftershocks and the mainshock were up to 34 km, which is larger than expected for an earthquake of this magnitude. Using data from South American stations and the relative location technique with Rayleigh waves (usually the clearest wave in noisy seismograms), the epicenters of the five largest aftershocks of Santa Cruz series, registered by the ISC, were determined in relation to the mainshock. This method enabled to achieve epicentral locations better than +/-2 km. Additionally, using data of three stations, two of the national network of Bolivia (MOC, and SIV), and LPAZ; the eight smallest aftershocks, recorded by the OSC, were relocated through correlation of P and S waves. The results show a N-S trend of the epicenters and an E dipping fault, the maximum distance between the aftershocks is less than 10 km, within the uncertainties of the fault subsurface rupture length, in accordance with the magnitude of the mainshock. Nevertheless the events are located away from the Mandeyapecua fault, one of the most important reverse fault in Bolivia; and present a different dipping, demonstrating that these events were generated by another fault of the area, that had not been well studied yet