HR: 15:05h
AN: S22D-06
TI: Probabilistic earthquake location
and 3-D velocity models in routine earthquake location
AU: * Lomax, A
EM: alomax@free.fr
AF: Scientific Software, 161 Allee du
Micocoulier, Mouans-Sartoux, 06370 France
AU: Husen, S
EM: husen@seismo.ifg.ethz.ch
AF: Swiss Seismological Service, ETH
Hoenggerberg, Zurich, 8093 Switzerland
AB:
Earthquake monitoring agencies, such as local networks or CTBTO, are
faced with the dilemma of providing routine earthquake
locations in near real-time with high precision and meaningful
uncertainty information. Traditionally, routine earthquake
locations are obtained from linearized inversion using layered seismic
velocity models. This approach is fast and simple.
However, uncertainties derived from a linear approximation to a set of
non-linear equations can be imprecise, unreliable, or
even misleading. In addition, 1-D velocity models are a poor
approximation to real Earth structure in tectonically complex
regions. In this paper, we discuss the routine location of earthquakes
in near real-time with high precision using
non-linear, probabilistic location methods and 3-D velocity models. The
combination of non-linear, global search algorithms
with probabilistic earthquake location provides a fast and reliable
tool for earthquake location that can be used with any
kind of velocity model. The probabilistic solution to the earthquake
location includes a complete description of location
uncertainties, which may be irregular and multimodal. We present
applications of this approach to determine seismicity in
Switzerland and in Yellowstone National Park, WY. Comparing our
earthquake locations to earthquake locations obtained using
linearized inversion and 1-D velocity models clearly demonstrates the
advantages of probabilistic earthquake location and 3-D velocity
models. For example, the more complete and reliable uncertainty
information of non-linear, probabilistic earthquake location greatly
facilitates the identification of poorly constrained hypocenters. Such
events are often not identified in
linearized earthquake location, since the location uncertainties are
determined with a simplified, localized and approximate
Gaussian statistic.
DE: 7215 Earthquake parameters
DE: 7230 Seismicity and seismotectonics
DE: 7260 Theory and modeling
SC: S
MN: 2003 Fall Meeting
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