Initial reference models in local earthquake tomography
TLDR
In this article, the same inversion formalism was used to determine hypocenters and one-dimensional (1-D) velocity model parameters, including station corrections, as the first step in the 3D modeling process.Abstract:
The inverse problem of three-dimensional (3-D) local earthquake tomography is formulated as a linear approximation to a nonlinear function. Thus the solutions obtained and the reliability estimates depend on the initial reference model. Inappropriate models may result in artifacts of significant amplitude. Here, we advocate the application of the same inversion formalism to determine hypocenters and one-dimensional (1-D) velocity model parameters, including station corrections, as the first step in the 3-D modeling process. We call the resulting velocity model the minimum 1-D model. For test purposes, a synthetic data set based on the velocity structure of the San Andreas fault zone in central California was constructed. Two sets of 3-D tomographic P velocity results were calculated with identical travel time data and identical inversion parameters. One used an initial 1-D model selected from a priori knowledge of average crustal velocities, and the other used the minimum 1-D model. Where the data well resolve the structure, the 3-D image obtained with the minimum 1-D model is much closer to the true model than the one obtained with the a priori reference model. In zones of poor resolution, there are fewer artifacts in the 3-D image based on the minimum 1-D model. Although major characteristics of the 3-D velocity structure are present in both images, proper interpretation of the results obtained with the a priori 1-D model is seriously compromised by artifacts that distort the image and that go undetected by either resolution or covariance diagnostics.read more
Citations
More filters
Journal ArticleDOI
A Double-Difference Earthquake Location Algorithm: Method and Application to the Northern Hayward Fault, California
TL;DR: In this paper, a least square solver is found by iteratively adjusting the vector difference between hypocentral pairs to minimize residuals between observed and theoretical travel-time differences.
Journal ArticleDOI
Double-Difference Tomography: The Method and Its Application to the Hayward Fault, California
TL;DR: In this paper, a double-difference (DD) seismic tomography method was developed that makes use of both absolute and relative arrival times to produce an improved velocity model and yields event locations of a quality equivalent to those of the DD location method.
Journal ArticleDOI
Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection
TL;DR: Using seismicity and hydrogeological models, it is shown that fluid migration from high-rate disposal wells in Oklahoma is potentially responsible for the largest swarm of earthquakes in the central United States.
Journal ArticleDOI
SeisAn Earthquake Analysis Software
Jens Havskov,Lars Ottemöller +1 more
TL;DR: The SeisAn database is a way of organizing data by using the directory and file structure, and is not a relational data system with general access techniques such as SQL, which usually is meant by the term “database.”
Journal ArticleDOI
Upper mantle structure beneath the Alpine orogen from high‐resolution teleseismic tomography
TL;DR: In this article, the authors performed high-resolution teleseismic tomography with manually picked P wave arrival times from seismograms recorded in the greater Alpine region, and the resulting data set consists of 4199 relative P wave arrivals and 499 absolute P wave Arrivals from 76 teleseismsic events, corrected for the contribution of the Alpine crust to the travel times.
References
More filters
OtherDOI
HYPO71 (revised; a computer program for determining hypocenter, magnitude, and first motion pattern of local earthquakes
Journal ArticleDOI
Finite-difference calculation of travel times
TL;DR: In this article, the travel times of the first arriving seismic waves through any velocity structure can be rapidly computed on a two- or three-dimensional numerical grid by finite-difference extrapolation from point to point.
Journal ArticleDOI
A fast algorithm for two-point seismic ray tracing
Junho Um,Clifford H. Thurber +1 more
TL;DR: In this article, an initial path estimate is perturbed using a geometric interpretation of the ray equations, and the travel time along the path is minimized in a piecewise fashion, iteratively performed until the travel times converges within a specified limit.
Journal ArticleDOI
Mapping the lower mantle: Determination of lateral heterogeneity in P velocity up to degree and order 6
TL;DR: In this article, the authors used the International Seismological Centre bulletins for the years 1964-1979 to derive a three-dimensional model of lateral variations of the P velocity in the lower mantle.
Journal ArticleDOI
Determination of three‐dimensional velocity anomalies under a seismic array using first P arrival times from local earthquakes: 1. A homogeneous initial model
Keiiti Aki,William H. K. Lee +1 more
TL;DR: In this paper, the effect of P velocity variation along the ray paths in three dimensions was modeled by rectangular blocks, and a parameter was assigned to each block describing the perturbation of P wave slowness in the block.