Showing papers on "Mohorovičić discontinuity published in 2012"

Estimating a Continuous Moho Surface for the California Unified Velocity Model

Abstract: 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 …

A three-dimensional Moho depth model for the Tien Shan from EGM2008 gravity data

Abstract: [1] The Tien Shan in Central Asia is the largest intracontinental mountain range in the world, but it is 1500 km away from the collision zone between the Indian and Eurasian plates. This region has been and still is the focus of numerous geoscientific studies, mainly because of its evolutionary history and its unique position in the Eurasian lithosphere plate. So far, mainly seismological data have been used to explore the origin of and ongoing seismic activity in this region, but only one study has investigated terrestrial gravity data. In this study, a new gravity data set, EGM2008, is used to determine the crust-mantle boundary (Mohorovicic discontinuity, Moho) of the Tien Shan using inversion of gravity data. In addition, an isostatic Moho is calculated from topographic data, which by comparison to the results of the gravity inversion illuminates the effects of isostatic compensation. The results of the gravity inversion generally agree with results of previous seismic studies and indicate that the Tien Shan has a mountain root with a thickness of about 75 km. Furthermore, the Moho is shallow under the basins, e.g., in the Tarim and Ili basins. The comparison with the isostatic Moho indicates an over-compensation of the orogen and an under-compensation of the basins. The over-compensation results from the former subduction of the Tarim Basin terrane in the south. The under-compensation of the Tarim Basin is generated by support of the terrane between the Tien Shan in the north and the Pamir mountains, Tibet and Himalayas in the south.