Crustal images from San Juan, Argentina, obtained using high frequency local event receiver functions

Images of the crust and upper mantle obtained using teleseismic receiver functions exhibit a weak P-S conversion from the Moho in Western Argentina, where a segment of the subducting Nazca plate flattens out beneath the overriding South American plate. To better estimate depth to the Moho and search for mid-crustal impedance contrasts, we calculate high frequency receiver functions using 37 intermediate-depth local earthquakes. Radial receiver functions from a station located near San Juan, Argentina, show a strong signal from the Moho at 7 seconds corresponding to a depth near 50 km, and conversions from interfaces within the crust at depths of similar to 20 and 35 km. The higher frequency results obtained using local events have twice the vertical resolution of the teleseismic results and the combined data sets indicate a gradational increase in S velocity in the lower crust that cannot be detected in the lower frequency teleseismic data alone.