Sayarim Experiment.

Sayarim Experiment. (2005) Aug 2009 ? ( 80 tons!... 11 holes!...) The GII Seismology Division has successfully conducted a series of experimental explosions with variable charge in the Sayarim Valley near Eilat, Israel (under the supervision of Dr.Y. Gitterman). The largest shot, 32.5 tons (see photo , courtesy of Dr. Y.Bartov) designed as a large-scale in-land seismic calibration explosion, intended to improve regional velocity models for calculating travel times of seismic waves to local and regional seismic stations and calibration of IMS stations. The explosion is part of the joint project of NRA, Jordan, GII, Israel and LLNL, USA: Seismic Calibration Using Mining Explosions in the Middle East, supported by the MERC program of the U.S.AID (PI - Dr. R.Hofstetter). Two smaller experimental explosions 0.3 ton and 2 tons (see photo) of 2-ton shot) were also conducted on June 13 and June 15, respectively, at the same site, in single boreholes of the same depth and diameter, thus providing (together with the calibration shot) a series for the yield-dependent analysis of regional waveforms. This experiment is part of the DOE/NNSA project: Seismic energy generation and partitioning into various regional phases from different seismic sources in the Middle East region (PI - Dr. Y.Gitterman). Ground Truth parameters of the explosions are presented in Table 1. The explosion site was located on land with the Massif Eilat Nature Reserve (see map . Geologically the area represents a graben filled by Quaternary alluvial conglomerates, underlined by consolidated limestone, chalk and chert rocks of the Cretaceous Mishash Formation (see a geological map ). A seismic refraction survey was conducted on the site by the GII team (supervisor Dr. M. Ezersky) before the experiment – to estimate thickness of near-surface soft sediments for evaluation drilling feasibility (for planned borehole large diameter and depth); and estimate a velocity model in the near-source zone (see survey results ). 13 large diameter boreholes (0.6-0.8 m) with depths of 17-21 m and spacing between holes about ~20 m, were drilled (Kodhim Shabat Ltd.) in dry alluvial subsurface layer (see photos of drilling machine, inner view of a hole and . cardboard casing The boreholes were filled with ANFO explosive (see photo of mix machines ), and fully loaded with stemming material. Detonation method design and explosion operations were fulfilled by blast manager Mr. Kobi Shimon (Arad Minerals Ltd.). The 300-kg explosion was fully contained, whereas two larger shots showed rock outburst and energy losses into the air (see video-clip of 2-ton shot and photo of 32.5 ton explosion from close location). The 2-ton explosion created a symmetric round crater of radius ~13-14 m, a number of different non-symmetric craters were created by the large explosion. Good waveform records were obtained for the explosion series in the near-source region by accelerometers at distances of 100-500 m (see an accelerogram sample for 300-kg shot) , and numerous portable and network seismic SP and BB stations in Israel and Jordan (see a map of recorded stations ). Clear Pn and Pg wave groups are observed at seismogram of the remote IMS array AS049 at Mt. Meron at distance ~ 350 km. Dry alluvium is commonly considered a low-coupling material (www.wws.princeton.edu/cgi-bin/byteserv.prl/~ota/disk2/1988/8838/883808.PDF)(see e.g. U.S. Congress, Office of Technology Assessment, Seismic Verification of Nuclear Testing Treaties, OTA-ISC-361, Washington, DC: U.S. Government Printing Office, Chapter 6, May 1988). However, local magnitudes ML estimated by the Israel Seismic Network stations showed that significant seismic strength was achieved for experiment explosions (ML~2 for 2 ton and ML~3 for 32.5 ton) in spite of non-consolidated sediment media accommodating the explosives and low charge depth, far from fully-contained conditions. Additional information about explosion design, and obtained measurements can be provided upon request (yefim@seis.mni.gov.il).