Uncertainties in standardized earthquake locations, which run into tens-of kilometers in many regions of the world, are a serious limitation to seismotectonic studies and nuclear treaty monitoring. For example, they preclude individual events from being confidently attributed with mapped surface faults, complicate the study of mainshock-aftershock sequences and triggering behavior, and errors in depth are problematic for establishing the mechanical and rheological properties of the crust. These errors mostly arise from unknown Earth velocity structure. Well-established relative multiple-earthquake relocation techniques help eliminate these errors, but it remains challenging to achieve bias-free absolute (‘calibrated’) locations.

In my research, I use an advanced multiple-earthquake relocation technique (mloc Engdahl & Bergman, 2000, Ritzwoller et al., 2003, Walker et al., 2011*) that utilizes calibration of discrete clusters of earthquakes by exploiting near source data, aftershock deployments and InSAR observations. This technique focuses on achieving calibrated, absolute earthquake locations that have reduced epicenter uncertainties (< 5 km), improved focal depth resolution, and well-characterized hypocentral uncertainty.

The map below shows the calibrated earthquake locations done so far in Iran and Turkey. Please visit the GCCEL website for a complete and up-to-date Global Catalog of Calibrated Earthquake Locations.


*Engdahl, R. E., Jackson, J. A., Myers, S. C., Bergman, E. A., & Priestley, K. 2006. Relocation and assessment of seismicity in the Iran region. Geophys. J. Int., 167, 761-778.

Ritzwoller, M. H., Shapiro, N. M., Levshin, A. L., Bergman, E. A., & Engdahl, E. R. 2003. Ability of a global three-dimensional model to locate regional events. J. Geophys. Res., 108.

Walker, R. T., Ramsey, L. A., & Jackson, J. 2011. Geomorphic evidence for ancestral drainage patterns in the Zagros Simple Folded Zone and growth of the Iranian plateau. Geol. Mag., 148, 901-910.