Forearc motion and deformation between El Salvador and Nicaragua: GPS, seismic, structural, and paleomagnetic observations
Forearc motion and deformation between El Salvador and Nicaragua: GPS, seismic, structural, and paleomagnetic observations
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DOI：
10.1130/l108.1
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发表时间：
2011-02-01
期刊：
影响因子：
2.4
通讯作者：
Correa-Mora, F.
中科院分区：
文献类型：
--
作者：
Alvarado, D.;DeMets, C.;Correa-Mora, F.
我们结合联合收割机的大地测量，结构，和古地磁数据从萨尔瓦多与全球定位系统（GPS）数据从洪都拉斯南部和尼加拉瓜来描述运动的萨尔瓦多和萨尔瓦多的前弧，并确定的位置和风格的断层横跨丰塞卡湾东部的火山弧的萨尔瓦多和尼加拉瓜西部。在萨尔瓦多萨尔瓦多、洪都拉斯南部和尼加拉瓜的35个地点对GPS测量值进行的元素建模表明，在加勒比板块参考框架中，萨尔瓦多和萨尔瓦多的前弧都以15 +/- 2 mm/年（-1）（95%极限）的速度平行于各自的海沟从西向西北移动。两个前弧的相似运动，尽管在它们下面的俯冲的倾斜度上有类似的20度-25度的差异，并且在萨尔瓦多萨尔瓦多近海没有任何明显的会聚倾斜度，但与最近的一个假设一致，即萨尔瓦多前弧将萨尔瓦多前弧推向西北，可能是由于中美洲前弧从其与哥斯达黎加近海科科斯海脊的碰撞区向西北侧逃逸所致。丰塞卡湾和邻近的萨尔瓦多东部萨尔瓦多形成了一个类似于60公里宽的伸展带，东西向延伸，由弥散地震活动、GPS速度和许多年轻的南北走向正断层确定，这些正断层由10米数字高程模型（DEM）、结构测量和激光雷达（光探测和测距）绘制。丰塞卡拉分构造中的走滑地震和丰塞卡拉分构造中33个地点的古地磁测量中的适度（类似于10度）垂直轴断块旋转的证据都表明伸展可能伴随着书架断层。
We combine geodetic, structural, and paleomagnetic data from El Salvador with Global Positioning System (GPS) data from southern Honduras and Nicaragua to describe the motions of the Salvadoran and Nicaraguan forearcs and determine the location and style of faulting across the Gulf of Fonseca offset of the volcanic arcs of eastern El Salvador and western Nicaragua. Finite-element modeling of GPS measurements at 35 sites in El Salvador, southern Honduras, and Nicaragua indicates that the Nicaraguan and Salvadoran forearcs both move west to northwest, parallel to their respective trenches, at 15 +/- 2 mm yr(-1) (95% limit) in a Caribbean plate reference frame. The similar motions of the two forearcs, despite an similar to 20 degrees-25 degrees difference in the obliquity of subduction beneath them and absence of any significant convergence obliquity offshore from El Salvador, are consistent with a recent hypothesis that the Nicaraguan forearc pushes the Salvadoran forearc to the northwest, possibly driven by northwestward lateral escape of the Central America forearc from its collision zone with the Cocos Ridge offshore from Costa Rica. The Gulf of Fonseca and adjacent eastern El Salvador form an similar to 60-km-wide extensional zone with E-W elongation, determined by diffuse seismicity, GPS velocities, and numerous young, N-S-striking normal faults mapped with a 10 m digital elevation model (DEM), structural measurements, and Lidar (light detection and ranging). Strike-slip earthquakes in the Fonseca pull-apart structure and evidence for modest (similar to 10 degrees) vertical-axis fault block rotations from paleomagnetic measurements at 33 sites in the Fonseca pull-apart structure both indicate that extension may be accompanied by bookshelf faulting.