IMPROVED GROUND TRUTH IN SOUTHERN ASIA USING IN-COUNTRY DATA, ANALYST WAVEFORM REVIEW, AND ADVANCED ALGORITHMS

摘要: A new catalog of seismicity at magnitudes above 2.5 for the period 1923-2008 in Iran region is assembled from arrival times reported by global, regional, and local seismic networks. Using in-country data we have formed events, mostly lower that were not previously included standard global earthquake catalogs. The magnitude completeness varies strongly through time, complete to about 4.2 prior 1998 reaching a minimum 3.6 during 1998-2005. Of 25,722 events catalog, most larger been carefully reviewed proper phase association, especially depth phases eliminate outlier readings, relocated. To better understand quality set Iranian networks are central this study, many waveforms re-picked an experienced analyst. Waveforms regional distances often complex. For makes time picks difficult make, smaller resulting can be substantially improved Even when signal/noise ratio large, re-picking lead significant differences.more » Picks made our analyst compared with original In spite obvious outliers, median (-0.06 s) spread (0.51 small, suggesting reasonable confidence placed Iran. This has used assess focal distributions throughout principal result study geographic pattern revealed relatively small number earthquakes (~167) depths constrained waveform modeling (+/- 4 km) now agreement much (~1229) determined using reanalysis ISC arrival-times (+/-10 km), within their respective errors. advance, as outliers future apparently anomalous readily identified and, if necessary, further investigated. patterns reliable interpreted context Middle Eastern active tectonics. Most continental lithosphere occur upper crust, less than 25-30 km depth, crustal shortening produced collision accommodated entirely thickening distributed deformation rather subduction crust into mantle. However, intermediate-depth associated subducted slab do across Caspian Sea beneath Makran coast. multiple-event relocation technique, specialized use different kinds near-source data, calibrate locations 24 clusters containing 901 drawn catalog. absolute these fixed either comparing relocated mapped fault geometry, one or more cluster accurately located independently network aftershock deployment, InSAR determine rupture zone shallow earthquakes, some combination data. technique removes systematic bias single-event done teleseismic 624 calibrated location uncertainties 5 90% level (GT590). 21 (847 events) both origin calculate empirical travel times, relative 1-D model (ak135), investigate event station travel-time anomalies functions epicentral distance azimuth. Substantial seen which make accurate impossible unless observing stations very short (less 200 models account lateral heterogeneity region. Earthquake international agencies, based on systematically biased southwest accuracy 18-23 km, value achievable applying limits secondary azimuth gap. here provides important constraint would begin Earth structure region, permit networks, ones, obtain region.« less