Description
Crustal thicknesses provide valuable constraints on models for the tectonic development of the North American continental margin. Previous gravity and seismic refraction surveys in the Peninsular Ranges Batholith (PRB) have yielded poorly constrained and conflicting crustal thickness estimates, ranging from 26 km to 43 km The teleseismic receiver function provides reliable estimates of crustal thickness through the identification of the P-to-S conversion (Ps) at the Moho. In a study by Ichinose et al., ( 11'16) observed Ps arrivals from receiver functions at the latitude of San Diego imply a relatively flat deep Moho (~40 km) under the western PRB, and a steeply shallowing of the Moho to the east (~40 km to ~25 km) under the eastern PRB. In this study, crustal thicknesses were estimated through analysis of teleseismic receiver functions at five stations in the northern PRB between the Elsinore Fault Zone and the eastern margin of the batholith. From observed Ps arrivals and tomographic velocity models, a northeastward thinning of the crust is inferred. The crustal thickness at the southwestern end of the 60-km profile was found to be ~37 km, thinning to ~28 km at the northeastern end. Unlike the Airy isostacy model, Moho topography does not mirror surface topography. Data from the receiver functions suggest a shallower Moho by ~9 km beneath the topographic high. This may be indicative of isostatic rebound of the crust due to footwall unloading during Miocene extension.
