Definition of Exclusion Zones Using Seismic Data

The active Dead Sea Rift fault zone: a seismic wave-guide

“…Since the seismic stations located within the DSR displayed lower Q c values than stations situated on the Western flank, it demonstrates that at short epicentral distances, wave paths confined exclusively to the sedimentary basin have a higher scattering than wave paths that comprise a section along the material interface of the boundary fault zones and within solid bedrock. Similarly, Bartal et al (2000) noted that a weak event (M 2.7) located North of the Dead Sea, reached a tripartite microarray, located out of the DSR at an epicentral distance of 81.5 km, faster than predicted if it had followed the shortest path. In both cases, seismic loads or at least some part of them see their propagation efficiency enhanced, guided by the DSR substructure, they arrive faster at the target than anticipated and with signal amplitude higher than expected.…”

“…At a regional scale, S n and P g waves are reported to be filtered in the vicinity of the DSR (Rodgers et al, 1997). At a local scale, a monitoring array deployed in the Negev (Bartal et al, 2000), received microseisms located in the DSR faster than expected based on predictions using a direct path. These observations confirm previous coda wave studies showing a discrepancy between the DSR and the flank of the rift (van Eck, 1988).…”

“…In fact, the data from the 1988 Dead Sea (M 2.1) and 1973 Kinneret (M 4.5) earthquakes as well as most of the data for the 1995 Nuweiba earthquake (M b 6.25) was recorded in stations for which neither the nature of the soil nor the presence of disturbing geomorphologic features such as alluvial fans and playa, can be invoked. Furthermore, the fact that P -and S-phase arrivals seem to be mixed or even inverted as observed during the 1998 Dead Sea earthquake (Bartal et al, 2000), suggests that parts of the seismic load travel along non-direct but faster paths, possibly along the nearby DSR.…”

“…Within the framework of the seismic exclusion zone design, a tripartite microseismic array picked up the 9 October 1998, Dead Sea earthquake, which had a very low magnitude (M L 2.1) at a hypocentral distance of 81.5 km (Bartal et al, 2000).…”

“…In the Dead Sea area, the microseismic activity apparently observed directly above the undeformed sedimentary basin could have two sources. First, a number of events presently located within the DSB could, in fact, coincide with the boundary fault zones if the bias of event location (Bartal et al, 2000;Steinberg et al, 2001) due to travel time anomalies caused by the DSR is properly taken into consideration. Second, the origin of these epicenters could be a deeper area where both boundary fault zones coalesce under the DSB, provided the brittle-ductile transition zone extends deep enough.…”