CLOSE IN SCS AND SSCS REVERBERATIONS FROM THE 9 JUNE 1994 BOLIVIAN EARTHQUAKE

Recordings of the Bolivian Earthquake of 9 June, 1994 from two portabl e experiments were analyzed for ScS and sScS reverberations. These sta tions span the distance range 6 degrees - 22 degrees, sampling the man tle beneath South America along an EW line from the central Andes to t he Brasilian Craton. We used the CORE method to obtain path-averaged l ocations of the Moho and 400 and 660 km discontinuities. The average d epth for D-400 is 410km for the BANJO stations and 395km beneath Brazi l, and the value for D-660 is 700km for BANJO and 675km for BLSP, whil e the difference D-660-D-400 = Delta D is 290km and 280km respectively . These values are much larger than the global average (around 245km) and suggest 200 degrees - 300 degrees colder temperatures in the regio n sampled. This is most plausibly explained by the reduced temperature s in the slab and surrounding region. We also detect a significant dis continuity at 210 km depth, with a shear wave impedance increase of at least 5%. Finally, we observe systematic variations in duration betwe en P, ScS and sScS that can only be attributed to source finiteness. T hese observations constrain the inclination of an equivalent unilatera l rupture velocity vector to be -17 degrees (positive up from horizont al). Our rupture model is consistent with models derived from subevent analysis of the P wave arrivals, and implies a source extent of 72 km .