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本文利用较为完备的球体位错理论,结合4.5年的震后位移数据,优化了2011年日本MW9.0地震震源区岩石圈弹性层厚度与地幔黏滞性因子,更新了该强震断层余滑时空演化过程.首先,基于日本列岛215个均匀分布的GPS连续观测站震前2年与震后4.5年的观测数据,提取了2011年日本MW9.0地震引起的震后位移时空变化;接着,依据断层余滑衰减相对较快的特点,利用黏弹性球体位错理论对震后3~4.5年的GPS观测数据进行反复拟合,确定2011年日本MW9.0地震震源区地幔黏滞性系数和岩石圈弹性层厚度的最优解分别为6×1018 Pa·s和30 km;然后,从震后3年内GPS观测数据中剔除地幔黏滞性松弛效应,获取了断层余滑对应的震后位移场;最后,利用基于球体位错理论的反演算法,反演了2011年日本MW9.0地震断层余滑的时空演化过程.结果表明,2011年日本MW9.0地震引起的断层余滑在震后半年内变化显著,震后2年主震区域余滑基本停止,断层的两端存在一定的余滑效应,断层余滑的累计矩震级达到8.59;地震后4年,地幔黏滞性松弛效应对震后位移场的贡献在总体上超过断层余滑的贡献. 相似文献
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Surface rupture of the Cariaco July 09, 1997 earthquake on the El Pilar fault, northeastern Venezuela 总被引：1，自引：0，他引：1
This paper discusses the surface rupture of the Cariaco July 09, 1997 Ms 6.8 earthquake in northeastern Venezuela – located at 10.545°N and 63.515°W and about 10 km deep. The field reconnaissance of the ground breaks confirms that this event took place on the ENE–WSW trending onshore portion of the dextral El Pilar fault (between the Gulfs of Cariaco and Paria), which is part of the major wrenching system within the Caribbean–South America plate boundary zone. Dextral slip along this fault was further supported by the structural style of this rupture (en echelon right-lateral R shears connected by mole tracks at restraining stepovers) and by larger geometric complexities (pop-ups at Las Manoas and Guarapiche), as well as by the focal mechanism solutions determined for the event by several authors. This 1997 surface ruptre comprised two distinct sections, from west to east: (a) a main very conspicuous, continuous, 30-km-long, rather straight, 075°N-trending alignment of en echelon surface breaks, with a rather constant, purely dextral coseismic slip of about 25 cm, but reaching a maximum value of 40 cm slightly northwest of Pantoño; and (b) a secondary discontinuous, 10-km-long, boomerang-shaped rupture, with a maximum coseismic slip of 20 cm at Guarapiche. The onshore extent of the surface rupture totalled 36 km, but may continue westward underwater, as suggested by the very shallow aftershock seismicity. This aftershock activity also clearly defined the steep north dip of the fault plane along the western rupture, suggesting tectonic inheritance on this major fault.From many locals' accounts, the rupture seems to have propagated from Pantoño to the west (highly asymmetric bidirectionality). This suggests that earthquake nucleation happened at or near the Casanay–Guarapiche restraining bend and rupture quickly propagated westward, allowing only a small fraction to progress eastwards beyond the bend. Additionally, the large fraction of after-slip (or creep) released is to be related to such restraining bend, which seems to have partly locked slip during rupture. 相似文献
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