The March 25, 1990 (Mw = 7.0, ML = 6.8), earthquake at the entrance of the Nicoya Gulf, Costa Rica: Its prior activity, foreshocks, aftershocks, and triggered seismicity
The March 25, 1990 (Mw = 7.0, ML = 6.8), earthquake at the entrance of the Nicoya Gulf, Costa Rica: Its prior activity, foreshocks, aftershocks, and triggered seismicity
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1990年3月25日（Mw = 7.0，ML = 6.8），哥斯达黎加尼科亚湾入口处的地震：其前期活动、前震、余震和引发的地震活动
DOI：
10.1029/94jb03099
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发表时间：
1995
影响因子：
--
通讯作者：
W. Schillinger
中科院分区：
文献类型：
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作者：
M. Protti;K. McNally;J. Pacheco;V. González;C. Montero;J. Segura;J. Brenes;V. Barboza;E. Malavassi;F. Güendel;G. Simila;D. Rojas;A. Velasco;Antonio Mata;W. Schillinger
1990年3月25日13：22：55.6 UTC，在哥斯达黎加的尼科亚湾入口处发生了一次大地震（Mw = 7.0，ML = 6.8），在哥斯达黎加中部造成了相当大的破坏，并引起了人们对尼科亚地震空区（Nishenko，1989）是否破裂的极大兴趣。当地的全国地震台网记录了这次大地震前6年的活动，16小时的前震，主震及其余震。该网络由国立大学的哥斯达黎加火山和地震观测站（OVSICORI-UNA）和Charles F.位于圣克鲁斯的加州大学里希特地震实验室（CFRSL-UCSC）。我们从这个台网获得了高分辨率的位置，确定主震在9°38.5′N，84°55.6′W（深度为20.0 km），最大前震（MW = 6.0，1990年3月25日13：16：05.8 UTC）在9°36.4′N，84°57.1′W（深度为22.4 km）。我们发现，余震带邻接的尼科亚地震空区的东南边界，这表明地震空区没有破裂。自1984年4月安装本地台网至1990年3月24日，在哥斯达黎加最活跃的地区之一尼科亚湾入口处发生了近1900次震级从1.7级到4.8级的地震（318次震级大于3.0级）。3月25日的地震发生在该地区的西北边缘，在主震前16小时，一系列前震开始。余震的时空分布和主震破裂过程的方向性分析均表明主震破裂为东南向传播。主震破坏了一个面积约为600平方公里的凹凸体，7天后面积扩大到4000平方公里。我们提出的证据表明，破裂的凹凸是由海山俯冲。通过对西太平洋宽频带长周期P波和SH波的反演，得到了一种逆冲断层机制，其浅层面走向为292°，倾角为26°，倾角为88°，与科科斯板块向加勒比板块俯冲的结果一致。最大前震和主震的局部初动与此解一致。我们还提出的证据表明，1990年3月25日，地震触发并重新激活了几个地震群在中部哥斯达黎加和暂时减少的活动在震中区的1983年7月3日（Ms = 6.2），佩雷斯Zeledon地震。
On March 25, 1990 a large earthquake (Mw = 7.0, ML = 6.8) occurred at the entrance of the Nicoya Gulf, Costa Rica, at 1322:55.6 UTC, producing considerable damage in central Costa Rica and generating much interest about whether or not the Nicoya seismic gap (Nishenko, 1989) had broken. The local country-wide seismographic network recorded 6 years of activity prior to this large earthquake, 16 hours of foreshocks, the mainshock, and its aftershocks. This network is operated jointly by the Costa Rica Volcanological and Seismological Observatory at the National University (OVSICORI-UNA), and the Charles F. Richter Seismological Laboratory at the University of California, Santa Cruz (CFRSL-UCSC). We obtained high resolution locations from this network and located the mainshock at 9°38.5′N, 84°55.6′W (depth is 20.0 km) and the largest foreshock (Mw = 6.0, March 25, 1990, at 1316:05.8 UTC) at 9°36.4′N, 84°57.1′W (depth is 22.4 km). We find that the aftershock zone abuts the southeast boundary of the Nicoya seismic gap, suggesting that the seismic gap did not rupture. Since the installation of the local network in April 1984 to March 24, 1990, nearly 1900 earthquakes with magnitudes from 1.7 to 4.8 (318 with magnitude 3.0 or larger) have been located at the entrance of the Nicoya Gulf, one of the most active regions in Costa Rica. The March 25 earthquake occurred at the northwest edge of this region, where a sequence of foreshocks began 16 hours prior to the mainshock. The spatial-temporal distribution of aftershocks and directivity analysis of the mainshock rupture process using teleseismic records both indicate a southeast propagating rupture. The mainshock ruptured an asperity of approximately 600 km2 of area, with this area expanding to 4000 km2 after 7 days. We present evidence that suggests that the ruptured asperity is produced by the subduction of a seamount. Inversion of teleseismic broadband and long-period P and SH waves yields a thrust faulting mechanism with the shallow plane striking 292°, dipping 26°, and with a rake of 88°, in agreement with the subduction of the Cocos plate under the Caribbean plate. Local first motions for the largest foreshock and the mainshock agree with this solution. We also present evidence suggesting that the March 25, 1990, earthquake triggered and reactivated several seismic swarms in central Costa Rica and temporally decreased the activity in the epicentral area of the July 3, 1983 (Ms = 6.2), Perez Zeledon earthquake.