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Earthquake Location Lecture in Seismological Research Center of IIEES
Title: Earthquake Location Accuracy in the Iran Region
Presentation by: Dr.Eric Bergman
Date: 1388-2-15 (2009-5-5) 14:00(Local time)
Location: third floor of Main building-IIEES
Abstract:
We investigate the accuracy of routine earthquake locations in the Iran region,
using a multiple event relocation technique that has been specialized to use
different kinds of near-source data to calibrate the locations of clusters of
earthquakes drawn from a carefully-reviewed catalog of 25,722 earthquakes in the
region during the period 1923-2008. We have calibrated the locations of 23
clusters containing 892 events, of which the locations of 622 are known to 5 km
or better at the 90% confidence level (GT590). Using the GT590 events we
investigate the location accuracy of two global catalogs (ISC and EHB) and of
two Iranian national network catalogs. We also investigate location accuracy as
a function of network scale (i.e., station istances) and azimuthal coverage. For
22 clusters (875 events) that are calibrated in both location and origin time,
we calculate empirical travel times and investigate anomalies as a function of
epicentral distance and azimuth, relative to a standard 1-D travel time model
(ak135). Substantial travel-time anomalies are seen in the Iran region which
make accurate locations impossible unless observing stations are at very short
distances (less than about 200 km) or travel-time models are improved to account
for lateral heterogeneity in the region. The arrival time data sets of the
calibrated earthquake locations reported here can be used to develop both
improved travel-time models and to constrain models of the 3-D structure of the
crust and upper mantle in the Iran region.
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