Accession Number ADA568670
Title Crustal and Upper Mantle Structure from Joint Inversion of Body Wave and Gravity Data.
Publication Date Sep 2012
Media Count 12p
Personal Author C. Rowe E. A. Bergman M. Maceira
Abstract We present a preliminary model of the three-dimensional seismic structure of the Iran region obtained via simultaneous, joint inversion of body wave travel time and gravity observations. The body wave data set is derived from location calibration efforts and includes a large (>1000 events) subset of GT5-level events. The arrival time data sets for these events include many readings of direct crustal P and S phases, as well as regional (Pn and Sn) and teleseismic phases. These data have been groomed to identify and remove outlier readings; empirical reading errors are estimated for most arrivals from multiple event relocation analysis. We use both free-air and Bouguer gravity anomalies derived from the global gravity model of the GRACE satellite mission. The gravity data provide information on shallow density variations with short spatial wavelengths, and deeper density structures with longer spatial wavelengths. To increase the usefulness of the gravity data, we apply high-pass filtering, yielding gravity anomalies that possess higher resolving power for crustal and lithospheric structures. To integrate both data sets into a single inversion a functional relationship between seismic velocities and density is required. We first use a combination of two empirical relations: one most appropriate for sedimentary rocks, and a linear Birch's Law that is more applicable to basement rocks. These relationships, however, assume a constant Poisson ratio throughout the inversion. We therefore also apply a method that allows the Poisson ratio to vary by mapping densities to VP and VS independently for different earth materials. Final results of the simultaneous inversion will help us to better understand the crustal and lithospheric structures associated with early-stage continental collision. Such models also provide an important starting model for computationally more expensive and time- consuming fully 3D waveform inversions.
Keywords Body wave
Earth crust
Earth mantle
Gravity
Seismic velocity
Seismic waves
Structural geology
Travel time


 
Source Agency Non Paid ADAS
NTIS Subject Category 48F - Geology & Geophysics
Corporate Author Los Alamos National Lab., NM.
Document Type Technical report
Title Note Conference paper.
NTIS Issue Number 1312
Contract Number FA9453-11-1-0233

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