ALBERT

Description: Strong motion data is not common around the Dead Sea region. Therefore, calibrating a new attenuation equation is a considerable challenge. However, the Holy Land has a remarkable historical archive, attesting to numerous regional and local earthquakes. Combining the historical record with modern measurements will enhance the regional equation. On 11 July 1927, a crustal rupture generated a moderate 6.25ML earthquake around the northern part of the Dead Sea. Up to five hundred people were killed and extensive destruction was recorded, even at places as far as 150 kilometers from the focus. We consider local near-surface properties, in particular, the shear-wave velocity, as an amplification factor. Where the shear-wave velocity is low, the seismic intensity at places far from the focus would likely be greater than expected from a standard attenuation curve. In this work, we used the Multi Analysis of Surface Waves (MASW) method to estimate seismic wave velocity at anomalous sites in Israel in order to calibrate a new attenuation equation for the Dead Sea region, based on 1927 macroseismic data integrated with modern measurements. Our new attenuation equation contains a term which quantifies solely lithological effects, whilst factors such as building quality, foundation depth, topography, earthquake directivity, type of fault, etc., remained out of the equation. Nonetheless, about 60% of the measured anomalous sites fit expectations and better fitting is achieved compared to other relevant attenuation equations. From a local point of view, this is the first time that an integration between historical data and modern seismic measurements improves the attenuation relation for the Dead Sea region. In the wider context, regions of low-to-moderate seismicity should use historical earthquake data together with modern measurements in order to better estimate the peak ground acceleration or the seismic intensities caused by future earthquakes. This integration will conceivably lead to a better understanding of future earthquakes and improve maps of seismic risk.