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Journal of Seismology

, Volume 22, Issue 6, pp 1529–1547 | Cite as

Regional minimum 1-D P-wave velocity model for a new seismicity catalogue with precise and consistent earthquake locations in southern Iran

  • H. Kianimehr
  • E. Kissling
  • F. Yaminifard
  • M. Tatar
ORIGINAL ARTICLE
  • 89 Downloads

Abstract

For faster and more robust ray tracing in 1-D velocity models and also due to the lack of reliable 3-D models, most seismological centers use 1-D models for routine earthquake locations. In this study, as solution to the coupled hypocenter-velocity problem, we compute a regional P-wave velocity model for southern Iran that can be used for routine earthquake location and also a reference initial model for 3-D seismic tomography. The inversion process was based on travel time data from local earthquakes paired reports obtained by merging the catalogues of Iranian Seismic Center (IRSC, 6422 events) and by the Broadband Iranian National Seismic Network (BIN, 4333 events) for southern Iran in the period 2006 through July 2017. After cleaning the data set from large individual reading errors and by identifying event reports from both networks belonging to same earthquake (a process called event pairing), we obtained a data set of 1115 well-locatable events with a total number of 24,606 P-wave observations. This data set was used to calculate a regional minimum 1-D model for southern Iran as result of an extensive model search by trial-and-error process including several dozens of inversions. Significantly different from previous models, we find a smoothly increasing P-velocity by depth with velocities of 5.8 km/s at shallow and velocities of 6.4 km/s at deepest crustal levels. For well-locatable events, location uncertainties are estimated in the order of ± 3 km for epicenter and double this uncertainty for hypocentral depth. The use of the minimum 1-D model with appropriate station delays in routine hypocenter location processing will yield a high-quality seismic catalogue with consistent uncertainty estimates across the region and it will also allow detection of outlier observations. Based on the two catalogues by IRSC and BIN and using the minimum 1-D model and station delays for all stations in the region, we established a new combined earthquake catalogue for southern Iran. While the general distribution of the seismicity corresponds well with that of the two individual catalogues by IRSC and BIN, the new catalogue significantly enhances the correlation of seismicity with the regional fault systems within and between the major crustal blocks that as an assembly build this continental region. Furthermore, the unified seismic catalogue and the minimum 1-D model resulting from this study provide important ingredients for seismic hazard studies.

Keywords

Earthquake location Merging travel time Regional minimum 1-D P-wave velocity model Earthquake catalogue Southern Iran 

Notes

Acknowledgments

The data used in our study were kindly provided by IRSC and BIN seismological centers, and also we used phase information of some stations from Earthquake Monitoring Program of Oman (network code OM) which is handled by Sultan Qaboos University, and of stations from UAE networks got from their website: http://seismology.ncms.ae/. We are grateful to the staff of both IRSC and BIN who routinely picked and also let us know general information about stations. Maps and figures were plotted using the Generic Mapping Tools (Wessel and Smith 1998).

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Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.International Institute of Earthquake Engineering and Seismology (IIEES)TehranIran
  2. 2.Institute of Geophysics, Swiss Federal Institute of Technology, ETH, ZurichZurichSwitzerland

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