Modeling coseismic displacements resulting from SAR interferometry and GPS measurements during the 1997 Umbria-Marche seismic sequence
Modeling coseismic displacements resulting from SAR interferometry and GPS measurements during the 1997 Umbria-Marche seismic sequence
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对 1997 年翁布里亚-马尔凯地震序列期间 SAR 干涉测量和 GPS 测量产生的同震位移进行建模
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发表时间：
2000
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通讯作者：
A. Galvani
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作者：
S. Salvi;S. Stramondo;M. Cocco;M. Tesauro;I. Hunstad;M. Anzidei;P. Briole;P. Baldi;Eugenio Sansosti;G. Fornaro;R. Lanari;F. Doumaz;A. Pesci;A. Galvani
在这项研究中，我们分析了同震GPS位移和DInSAR数据，以约束1997年翁布里亚-马尔切地震序列中三次最大地震的位错模型。前两次事件分别发生在9月26日00:33 GMT （Mw 5.7）和09:40 GMT (Mw 6.0)，使用GPS位移和DInSAR干涉图进行了调查。我们讨论并比较了以前的研究结果，这些研究分别对较小的大地测量数据子集进行了建模。我们为这两次地震提供了一个位错模型，该模型与GPS和DInSAR数据都很好地拟合，并且与地震和地质调查结果一致。第一个事件是向东南方向的单侧断裂，并伴有均匀的错位。走向、前倾角和倾角是由CMT解决方案产生的。第二个事件包括向西北方向的单边破裂和断裂面上的可变滑动分布。走向和前倾角与CMT解一致，但倾角略有修改，以改善GPS和DInSAR数据的同时拟合。虽然第二次破裂（格林尼治标准时间09:40）非常接近地表，但对大地测量数据的拟合表明，尽管地表地质效应更明显，第一次破裂（格林尼治标准时间00:33）更深（2公里）。新的SAR干涉图分析可以识别出10月3日（Mw 5.2）和6日（Mw 5.4）地震事件造成的5-6厘米的额外位移。我们使用新的DInSAR干涉图数据来模拟1997年10月14日塞拉诺地震的位移场。对于这一事件，没有重要的GPS测量数据。我们测试了两种不同的断层平面几何形状：一种是盲的平面断层（顶部深度= 2.4 km），另一种是到达地表的弯曲断层。这两个模型与数据的拟合大致相似，并表明大部分滑动是在深度大于2.4 km的缓坡（40°-45°）断层面上释放的。它们还表明，由于震源西北部有明显的地表变形，因此单侧破裂不允许拟合干涉条纹。此外，我们认为均匀滑动模式南部高残差的集中实际上可能表明该地区存在一定的滑动变异性。我们得出的结论是，尽管震级适中且缺乏明显的地表断层，但空间大地测量数据允许约束位错模型，为该层序中三个最大事件的破裂过程提供了新的见解。
In this study we analyse coseismic GPS displacements and DInSAR data to constrain a dislocation model for the three largest earthquakes of the 1997 Umbria-Marche seismic sequence. The first two events, which occurred on September 26 at 00:33 GMT (Mw 5.7) and 09:40 GMT (Mw 6.0) respectively, are investigated using both GPS displacements and DInSAR interferograms. We discuss and compare the results of previous studies which separately modeled a smaller subset of geodetic data. We provide a dislocation model for these two earthquakes which fits well both GPS and DInSAR data and agrees with the results of seismological and geological investigations. The first event consists of a unilateral rupture towards the southeast with a uniform dislocation. The strike, rake and dip angles are those resulting from the CMT solution. The second event consists of an unilateral rupture towards the northwest and a variable slip distribution on the fault plane. The strike and the rake are consistent with the CMT solution, but the dip angle has been slightly modified to improve the simultaneous fit of GPS and DInSAR data. While the second rupture (09:40 GMT) arrived very close to the surface, the fit to geodetic data shows that the first rupture (00:33 GMT) is deeper (2 km), despite the more evident surface geological effects. The analysis of new SAR interferograms allows the identification of a 5–6 cm additional displacement caused by the October 3 (Mw 5.2) and 6 (Mw 5.4) seismic events.We use data from a new DInSAR interferogram to model the displacement field of the Sellano earthquake of October 14, 1997. For this event significant GPS measurements were not available. We tested two different fault plane geometries: a blind, planar fault (top depth = 2.4 km), and a curved (listric) fault reaching the surface. The two models provide a generally similar fit to the data, and show that most of the slip was released at depths greater than 2.4 km along a gently dipping (40°–45°) fault surface. They also show that a unilateral rupture does not allow fitting the interferometric fringes since there is evident surface deformation to the northwest of the hypocenter. Moreover, we suggest that the concentration of high residuals in the southern part of our uniform slip model may in fact indicate a certain slip variability in this area.We conclude that, despite the moderate magnitudes and the lack of significant surface faulting, the space geodetic data allowed to constrain dislocation models giving new insights in the rupture process of the three largest events of the sequence.