Simulation of Seismic-Wave Propagation During the 1927 ML...
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2. Research Goals and Methodology e 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 distrib- uted over an elliptical rupture patch using a “pseudo-Gaussian” slip-size function (Figure 2). e DSM was implemented in a finite difference code (WPP 2.2) as a pure sinistral strike-slip mechanism rupturing mainly northward. e 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 down- ward for the computational domain (Figure 2). MMI (Wald et al., 1999) and EMS98/MSK64 (Grünthal, 1998; Medvedev et al., 1964) intensities were calculated based on synthetic seismograms (Figure 3) produced at reported intensity localities and compared to the reported intensities (Figure 4). Figure 3: (a) Synthetic seis- mograms of vertical com- ponent ground velocity and (b) calculated PGV at reported localities sorted by epicentral distance. Figure 4: (a) Reported and predicted intensities (MMI and EMS) with curve fit- ting using Stromeyer and Grünthal, (2009) aenua- tion relations for macro- seismic intensities. (b) Re- ported minus Predicted in- tensities. (c) Histogram of difference distribution for reported minus predicted intensities. Figure 2: (a) and (b) Slip size and rupture time of the DSM used for initiating seismic-wave propagation. (c) Density and seismic velocities used for the laterally homogeneous seismic model, and (d) the 3D volume with surface topography and P-wave velocity. G E O L O G I C A L S U R V E Y O F I S R A E L Earthquake Simulations Cluster .gsi.gov.il Simulation of Seismic-Wave Propagation During the 1927 M L 6.25 Jericho Earthquake Shahar Shani-Kadmiel1,3,*, Michael Tsesarsky1,2, and Zohar Gvirtzman3 1 Department of Geological and Environmental Sciences, BGU; 2 Department of Structural Engineering, BGU; 3 Geological Survey of Israel 1. Introduction e 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. e M L 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. 132 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-aributes: construc- tion quality, topographic slope, groundwater level, and surface geology (Figure 1). 3. Results Synthetic seismograms sorted by epicentral distance are presented in Figure 3a and calculated PGV values in Figure 3b. Considering the simplicity of the velocity model, the agreement between the computed and reported seismic intensities is surprisingly good with a mode 0 difference distribu- tion relative to the EMS98 scale and more than 90% of the values within a single intensity unit differ- ence (Figure 4). Intensities computed according to the MMI scale underestimate the reported inten- sities with mode 1. 4. Summary and Conclusions At a first glance, the seismic radiation paern and directivity effect of the rupture as dipicted by the PGV in Figure 5 explain the reported intensities quite well. is would not have been the case had the fault ruptured southward as previously suggested by Ben-Menahem et al. (1976) and others. e predicted EMS98/MSK64 values were found to be in agreement with the reported intensity values whereas the predicted MMI values were found to consistently under-predict the reported in- tensity values. e discrepencies between the predicted and reported intensity values are aributed to local geo- logical structures and near surface velocity anomalies. We intend to further improve the accuracy of intensity prediction by using increasingly accurate geological models. 0 30 60 90 120 150 180 epicentral distance, km 3 4 5 6 7 8 9 intensity Reported MMI EMS 0 30 60 90 120 150 180 epicentral distance, km −3 −2 −1 0 1 2 3 4 5 reported - predicted MMI EMS 0 10 20 30 40 50 frequency −3 −2 −1 0 1 2 3 4 5 MMI EMS 0 20 40 60 80 100 120 140 160 180 epicentral distance, km 0 20 40 60 80 100 time since origin, s 0 30 60 90 120 150 180 epicentral distance, km 0 10 20 30 40 50 60 70 PGV, cm/sec a c e b a b d 0 1 2 3 4 5 6 7 0 2 4 6 8 10 12 depth, km V p ; km=s V s ; km=s ½; gr=cm 3 P-wave velocity, m/s a c b d Figure 5: Predicted PGV with a visi- ble northward directivity of the rup- ture process. * Contact: [email protected] (Shahar Shani-Kadmiel) NMEM2015 • July 5-9 • Smolenice Castle • Bratislava • Slovakia Geological Survey of Israel The Ministry of National Infrastructures Figure 1: (a) ,(b) and (c) Structural damage caused by the 1927 Jericho earthquake in Mount of Olives, Jerusa- lem, Winter Palace Hotel in Jericho, and Augusta Victoria Hospital, respectively. (d) Recorded seismogram of the event at the Royal Observatory of Belgium in Uccle. (e) Reported Intensities (aſter Zohar and Marco, 2012).
Transcript of Simulation of Seismic-Wave Propagation During the 1927 ML...
2. Research Goals and Methodology�e main goal of our research is to develop a generic and robust �nite 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 distrib-uted over an elliptical rupture patch using a “pseudo-Gaussian” slip-size function (Figure 2). �e DSM was implemented in a �nite di�erence code (WPP 2.2) as a pure sinistral strike-slip mechanism rupturing mainly northward. �e 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 �rst iteration, we used a laterally homogeneous velocity model starting at the surface topography and extending down-ward for the computational domain (Figure 2).
MMI (Wald et al., 1999) and EMS98/MSK64 (Grünthal, 1998; Medvedev et al., 1964) intensities were calculated based on synthetic seismograms (Figure 3) produced at reported intensity localities and compared to the reported intensities (Figure 4).
Figure 3: (a) Synthetic seis-mograms of vertical com-ponent ground velocity and (b) calculated PGV at reported localities sorted by epicentral distance.
Figure 4: (a) Reported and predicted intensities (MMI and EMS) with curve �t-ting using Stromeyer and Grünthal, (2009) a�enua-tion relations for macro-seismic intensities. (b) Re-ported minus Predicted in-tensities. (c) Histogram of di�erence distribution for reported minus predicted intensities.
Figure 2: (a) and (b) Slip size and rupture time of the DSM used for initiating seismic-wave propagation. (c) Density and seismic velocities used for the laterally homogeneous seismic model, and (d) the 3D volume with surface topography and P-wave velocity.
GEOLOGICAL SUR
VEY OF ISRAEL
Earthquake Simulations Cluster.gsi.gov.il
Simulation of Seismic-Wave Propagation Duringthe 1927 ML 6.25 Jericho Earthquake
Shahar Shani-Kadmiel1,3,*, Michael Tsesarsky1,2, and Zohar Gvirtzman31 Department of Geological and Environmental Sciences, BGU; 2 Department of Structural Engineering, BGU; 3 Geological Survey of Israel
1. Introduction�e 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.
�e ML 6.25 July 11, 1927 Jericho earthquake was the most destructive earthquake in the 20th century in the vicinity of Israel and the �rst signi�cant 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 �ow of the Jordan River had stopped for 21.5 h.
132 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-a�ributes: construc-tion quality, topographic slope, groundwater level, and surface geology (Figure 1).
3. ResultsSynthetic seismograms sorted by epicentral distance are presented in Figure 3a and calculated
PGV values in Figure 3b. Considering the simplicity of the velocity model, the agreement between the computed and reported seismic intensities is surprisingly good with a mode 0 di�erence distribu-tion relative to the EMS98 scale and more than 90% of the values within a single intensity unit di�er-ence (Figure 4). Intensities computed according to the MMI scale underestimate the reported inten-sities with mode 1.
4. Summary and ConclusionsAt a �rst glance, the seismic radiation pa�ern and directivity e�ect of the rupture as dipicted by the
PGV in Figure 5 explain the reported intensities quite well. �is would not have been the case had the fault ruptured southward as previously suggested by Ben-Menahem et al. (1976) and others.
�e predicted EMS98/MSK64 values were found to be in agreement with the reported intensity values whereas the predicted MMI values were found to consistently under-predict the reported in-tensity values.
�e discrepencies between the predicted and reported intensity values are a�ributed to local geo-logical structures and near surface velocity anomalies. We intend to further improve the accuracy of intensity prediction by using increasingly accurate geological models.
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* Contact: [email protected] (Shahar Shani-Kadmiel)NMEM2015 • July 5-9 • Smolenice Castle • Bratislava • Slovakia
Geological Survey of IsraelThe Ministry of National Infrastructures
Figure 1: (a) ,(b) and (c) Structural damage caused by the 1927 Jericho earthquake in Mount of Olives, Jerusa-lem, Winter Palace Hotel in Jericho, and Augusta Victoria Hospital, respectively. (d) Recorded seismogram of the event at the Royal Observatory of Belgium in Uccle. (e) Reported Intensities (a�er Zohar and Marco, 2012).
