HR: 0800h
AN: S41A-04    [Abstracts]
TI: Seismic-Wave Attenuation and Source Excitation in La Paz-Los Cabos, Baja California Sur, Mexico
AU: * Ortega, R
EM: ortega@cicese.mx
AF: Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Miraflores 334. Fracc. Bellavista, La Paz, BCS 23050, Mexico
AU: Gonzalez, M
EM: mgonzale@cicese.mx
AF: Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Km 107 Carretera Tijuana-Ensenada, Ensenada, BC 22860, Mexico
AB: We present results from a regional study of seismic-wave attenuation and source excitation from small- magnitude earthquakes recorded at distances from 6 to 180 km in the La Paz-Los Cabos region, at the south end of the Baja California Peninsula. Data were recorded using 32 strong-motion seismic stations from the La Paz network (LAP). A least squares regression separating the excitation, site, and propagation effects was carried out. We performed the analyses in the time and frequency domains, and we compared these results with results from a coda-normalization method. The propagation term was parameterized to represent a geometrical spreading function and a frequency-dependent Q(f) at a reference distance of 40 km. We estimated the regional attenuation by measuring the maximum amplitude of the S- or Lg-waves as a function of frequency, defining a continuous piecewise propagation term, D(r,f), after separating the excitation and site terms. Our results show that the attenuation is lower compared to that of central or northern Mexico. Recorded data were of remarkably good quality in spite of the fact that the strong-motion network recorded only small-size earthquake.
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Seismology [S]
MN: 2007 Joint Assembly