The Northwest Trending North Boquerón Bay‐Punta Montalva Fault Zone; A Through Going Active Fault System in Southwestern Puerto Rico
The Northwest Trending North Boquerón Bay‐Punta Montalva Fault Zone; A Through Going Active Fault System in Southwestern Puerto Rico
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西北走向的北博克龙湾-蓬塔蒙塔瓦断层带；波多黎各西南部的贯穿活动断层系统
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发表时间：
2013
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影响因子：
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通讯作者：
J. Joyce
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作者：
C. Roig;E. Asencio;J. Joyce
北博克隆湾-蓬塔蒙塔尔瓦断裂带已绘制成横跨波多黎各西南部拉哈斯山谷的地图。断层的识别是基于对地球物理数据、卫星图像和野外测绘的详细分析。断裂带由一系列白垩纪基岩断裂组成，中新世灰岩和第四系冲积扇沉积重新激活和变形。该断裂带地震活跃(当地震级大于5.0级)，有许多当地有震感的地震。震源机制解表明应变分配，主要是东西向的左旋位移，小的正断层主要向东北方向运动。在拉哈斯山谷南缘的第四系冲积扇沉积的断续溪流中，可以发现北东向的裂缝和正断层。拉哈斯山谷是一个东西走向的30公里长的断陷控制凹陷。冲积扇内的优先剥蚀区与北博克隆湾断层的陆上投影平行，倾向于西-西北方向。北博克隆湾断裂与拉哈斯山谷东南部的蓬塔蒙塔尔瓦断裂一致。这两条断裂都显示出中新世地层强烈的南倾。在西端，北博克隆湾断裂被平坦的全新世沉积所覆盖，而在南端，蓬塔蒙塔尔瓦断裂表现出河流排水的左旋位移，约为几百米。
The North Boqueron Bay-Punta Montalva fault zone has been mapped crossing the Lajas Valley in southwest Puerto Rico. Identification of the fault was based upon detailed analysis of geophysical data, satellite images, and field mapping. The fault zone consists of a series of Cretaceous bedrock faults that reactivated and deformed Miocene limestone and Quaternary alluvial fan sediments. The fault zone is seismically active (local magnitude greater than 5.0) with numerous locally felt earthquakes. Focal mechanism solutions suggest strain partitioning with predominantly east-west left-lateral displacements with small normal faults striking mostly toward the northeast. Northeast-trending fractures and normal faults can be found in intermittent streams that cut through the Quaternary alluvial fan deposits along the southern margin of the Lajas Valley, an east-west-trending 30-km-long fault-controlled depression. Areas of preferred erosion within the alluvial fan trend toward the west-northwest parallel to the onland projection of the North Boqueron Bay fault. The North Boqueron Bay fault aligns with the Punta Montalva fault southeast of the Lajas Valley. Both faults show strong southward tilting of Miocene strata. On the western end, the Northern Boqueron Bay fault is covered with flat-lying Holocene sediments, whereas at the southern end the Punta Montalva fault shows left-lateral displacement of stream drainage on the order of a few hundred meters.