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Geophysical Institute of Israel
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- PublicationRestrictedWeak-motion-based attenuation relationships for Israel(2008)
; ; ; ; ; ; ;Meirova, T.; Geophysical Institute of Israel ;Hofstetter, R.; Geophysical Institute of Israel ;Ben-Avraham, Z.; Geophysical Institute of Israel ;Steinberg, D.; Geophysical Institute of Israel ;Malagnini, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Akinci, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; We performed a regional study of earthquake ground motion scaling relations to provide the seismic hazard community of Israel with a new attenuation relationship that could be used for the prediction of earthquake-induced ground motion. Strong earthquakes are rather scarce in Israel and the existing collection of records from strong earthquakes is not sufficient to allowthe use of traditional regression methods to develop a regional attenuation relationship. We used velocity seismograms from the Israel Seismic Network to estimate the distance and frequency dependence of ground motion in the Israel region from frequent, smaller regional earthquakes. Our analyses included 4814 waveforms recorded by 30 stations of the Israel Seismic Network from 2000 to 2005. We restricted our analysis to 330 events recorded at five or more stations, with duration magnitudes ranging between 1.0 and 5.2. We derived empirical excitation, site and regional attenuation terms by regressing the peak amplitudes of narrowband-filtered seismograms around the shear wave arrivals and the rms Fourier spectral amplitudes taken around the specific sampling frequency. In order to optimize the attenuation parameters in our scaling model, we used a simple grid search. An optimal solution for minimal error between empirical and theoretical attenuation function was found for the quality parameter Q( f ) = 298 f^0.67 and the geometrical spreading g(r ) parametrized as a bilinear, piecewise function: r^−0.74 for r ≤ 60 km and r^−0.47 for r > 60 km. The spectral parameters κ of 0.015 s and stress drop increasing from 0.3 to 4 MPa were used to model the excitation spectra. A theoretical modelling effort based on Brune’s source spectrum and Random Vibration Theory (RVT) was performed on the attenuation and source parameters estimated in this study. Comparison of the attenuation relationship derived with locally measured ground motions shows excellent agreement with the data in the magnitude range forwhichwe have observations and seems to be adequate for predictions of earthquake ground motion for the Israel region. Comparison of Peak Ground Acceleration (PGA) predictions, based on our scaling relationship with those that have been recently used for seismic hazard analysis in Israel shows that our attenuation relationship predicts significantly lower ground motions than other relations.172 24 - PublicationOpen AccessAn Operational Earthquake Forecasting Experiment for Israel: Preliminary Results(2021-09)
; ; ; ; ; ; ; ; ; ; ; ; ; Operational Earthquake Forecasting (OEF) aims to deliver timely and reliable forecasts that may help to mitigate seismic risk during earthquake sequences. In this paper, we build the first OEF system for the State of Israel, and we evaluate its reliability. This first version of the OEF system is composed of one forecasting model, which is based on a stochastic clustering Epidemic Type Earthquake Sequence (ETES) model. For every day of the forecasting time period, January 1, 2016 - November 15, 2020, the OEF-Israel system produces a weekly forecast for target earthquakes with local magnitudes greater than 4.0 and 5.5 in the entire State of Israel. Specifically, it provides space-time-dependent seismic maps of the weekly probabilities, obtained by using a fixed set of the model’s parameters, which are estimated through the maximumlikelihood technique based on a learning period of about 32 years (1983–2015). According to the guidance proposed by the Collaboratory for the Study of Earthquake Predictability (CSEP), we also perform the N- and S-statistical tests to verify the reliability of the forecasts. Results show that the OEF system forecasts a number of events comparable to the observed one, and also captures quite well the spatial distribution of the real catalog with the exception of two target events that occurred in low seismicity regions.149 10