Estimating a Continuous Moho Surface for the California Unified Velocity Model

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Online material : Simple Matlab script to plot Moho profiles; continuous Moho surface; data points used to estimate the Moho surface. The Mohorovicic discontinuity (Moho) is a globally identifiable boundary between the crust and the uppermost mantle (Dziewonski and Anderson, 1981). It is detected using seismic techniques, such as reflected energy from local earthquakes (e.g., Richards-Dinger and Shearer, 1997) or active-source experiments (e.g., Christeson et al. , 2010) or from crustal reverberations of waves from distant earthquakes (e.g., Burdick and Langston, 1977; Zhu and Kanamori, 2000). Locally, the Moho surface may exhibit complexity in terms of both the magnitude and length scale of its variations in depth; furthermore, the impedance contrast across the Moho may also vary in terms of both the magnitude and length scales (Fig. 1). Body waves and surface waves from both teleseismic and local earthquakes, as well as seismic waves from active-source experiments, may be sensitive to the variations in the Moho. These seismic waves can be used within tomographic inversions to improve the characterization of Earth’s structure in the transition from crust to upper mantle. The Moho surface constitutes an integral part of any Earth model, from regional to global scales. The objective of this paper is to estimate a detailed Moho surface, from all available data, for onshore and offshore California; currently, no such map exists. Our motivation is to obtain a continuous, smooth surface that can be implemented within 3D structural models that are used for simulations of seismic-wave propagation (e.g., Komatitsch et al. , 2004; Tape, Liu, et al. , 2009), such as the California Community Velocity Model (CVM-H) of the Southern California Earthquake Center (SCEC; Suss and Shaw, 2003; Plesch et al. , 2011). We first document the available datasets for estimating the Moho surface in California …