干旱区生态环境知识资源中心

Seismic activity in Kuwait is found mainly in clusters originating in three localities as monitored by 8-station Kuwait Seismic Network (KSN): (a) Southern Oilfields (Ahmadi, Burgan, Magwa, Minagish, Umm Gudair), (b) Northern Oilfields (Sabriyah, Raudhatain) and (c) their intervening areas including the Kuwait Bay - Failaka Island. Seismic clusters dominate the first two areas, having produced small magnitude shocks. Based on instrumental records, the prominent earthquakes originating from the oilfields in Kuwait are the followings: June 2, 1993 (Lat. 28.88N, Long. 47.64E, h = 20 km, Mag. 4.7), June 4, 1994 (Lat. 28.98N, Long. 47.44E, h = 20 km, Mag. 3.2) and Aug. 17, 2007 (Lat. 28.53N, Long. 47.47E, h = 10 km, Mag. 4.3). The last earthquake at Kuwait - Saudi Arabia border originated in the neighbourhood of the Minagish and Umm Gudair Oilfields, where, the most significant structural feature in the subsurface is the Kuwait Arch that clearly continues southward into Saudi Arabia. We have argued elsewhere that seismic activity in Kuwaiti Oilfields or in their surroundings is an outcome, at least in part, of hydrocarbon fluid withdrawal or the man-made burning of oil fields and the consequent regional depletion of pore pressure causing massive subsurface rock failures (Bou-Rabee and Nur, 2002). That this may be a probable mechanism is corroborated by repeat (interferometric) synthetic aperture radar data recently analysed (by Saif ud din et al., 2006) for the Burgan Oilfield where subsidence by about 27 mm is noticed over a 3 year period. However, for one-to-one correspondence of oilfield seismic events to subsurface structures, it is important to improve upon the resolution of hypocentral parameter determination and source mechanisms as well to recognize the active faults or structures. A distinct progress in this direction has been to utilize the single-sensor seismic imaging technique for reservoir characterization in the Minagish Oilfield in south Kuwait by Shabrawi et al. (2005) that has the potentiality for time-lapse reservoir monitoring. On a broader scale, the environmental impact of induced seismicity in Kuwait Oilfields is probably linked to ground subsidence. Their environmental aspects in Kuwait are known to have different manifestations such as sinkhole subsidence in municipal areas or hydrogeologic sinkhole in the desert of Kuwait. However, to ascertain their exact details for seismic hazard evaluation to oilfield structures and municipal settlements in Kuwait, we require closer seismic monitoring of oilfields, time-lapse microgravity and GPS network data.