Title: Rapid estimation of earthquake locations using waveform traveltimes

Abstract

SUMMARY We introduce a new approach for locating earthquakes using arrival times derived from waveforms. The most costly computational step of the algorithm scales as the number of stations in the active seismographic network. In this approach, a variation on existing grid search methods, a series of full waveform simulations are conducted for all receiver locations, with sources positioned successively at each station. The traveltime field over the region of interest is calculated by applying a phase picking algorithm to the numerical wavefields produced from each simulation. An event is located by subtracting the stored traveltime field from the arrival time at each station. This provides a shifted and time-reversed traveltime field for each station. The shifted and time-reversed fields all approach the origin time of the event at the source location. The mean or median value at the source location thus approximates the event origin time. Measures of dispersion about this mean or median time at each grid point, such as the sample standard error and the average deviation, are minimized at the correct source position. Uncertainty in the event position is provided by the contours of standard error defined over the grid. An application of this technique tomore » a synthetic data set indicates that the approach provides stable locations even when the traveltimes are contaminated by additive random noise containing a significant number of outliers and velocity model errors. It is found that the waveform-based method out-performs one based upon the eikonal equation for a velocity model with rapid spatial variations in properties due to layering. A comparison with conventional location algorithms in both a laboratory and field setting demonstrates that the technique performs at least as well as existing techniques.« less

Authors:

Vasco, D. W.  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-1210-8628"

Nakagawa, Seiji ^[1]; Petrov, Petr ^[1]; Newman, Greg ^[1]

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+ Show Author Affiliations

1. Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA

Publication Date:

Fri Mar 01 00:00:00 EST 2019

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division

OSTI Identifier:

1503349

Alternate Identifier(s):

OSTI ID: 1572821

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Published Article

Journal Name:

Geophysical Journal International

Additional Journal Information:

Journal Name: Geophysical Journal International Journal Volume: 217 Journal Issue: 3; Journal ID: ISSN 0956-540X

Publisher:

Oxford University Press

Country of Publication:

United Kingdom

Language:

English

Subject:

58 GEOSCIENCES; Earthquake location; Earthquakes; Hypocentre, Seismicity