Simulation of seismic-wave propagation during the 1927 ML 6.25 Jericho earthquake

The Dead Sea Transform (DST) is the major seismic source in Israel and neighboring countries, with a proven seismic record: geological, archeological and historical. It is estimated to produce up to magnitude 7.5 earthquakes. However, due to the low seismicity rate and the limited deployment of seismological instrumentation, strong earthquakes and their ground motions were not recorded in the region. The ML 6.25 July 11, 1927 Jericho earthquake was the most destructive earthquake in the 20th century in the vicinity of Israel and the first significant one to be recorded worldwide. Estimations of casualties range between 250-500 death and 400-700 injuries. Many buildings were damaged (Figure 1), landslides and rockfalls were observed and the flow of the Jordan River had stopped for 21.5 h. 133 Intensity records, based on physical evidences and reports, were compiled by Avni et al., (2002) and re-evaluated by Zohar and Marco (2011) to account for local site-attributes: construction quality, topographic slope, groundwater level, and surface geology. The main goal of our research is to develop a generic and robust finite source model for initiating seismic-wave propagation in simulations of strong earthquakes in regions with low seismicity rate and/or limited instrumental coverage. To this end we have developed the kinematic Distributed Slip Model (DSM), where slip is distributed over an elliptical rupture patch using a “pseudo-Gaussian” slip-size function. The DSM was implemented in a finite difference code (WPP 2.2) as a pure sinistral strike-slip mechanism rupturing mainly northward. The computational domain was discretized into 6.3E8 grid points and 30,000 time steps at a temporal resolution of 6.6 milliseconds were computed. As a first iteration, we used a laterally homogeneous velocity model starting at the surface topography and extending downward for the computational domain. EMS98/MSK64 (Grünthal, 1998; Medvedev et al., 1964) intensities were calculated based on synthetic seismograms produced at reported intensity localities and compared to the reported intensities. Distribution of residuals shows that 56% of the calculated intensities match the reported intensities and that 98% of the calculated intensities are within a single unit from the reported intensities. The RMS of intensity residuals for the 122 points is 0.68.