Central Costa Rica deformed belt: Kinematics of diffuse faulting across the western Panama block
Central Costa Rica deformed belt: Kinematics of diffuse faulting across the western Panama block
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哥斯达黎加中部变形带：巴拿马地块西部扩散断层运动学
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
T. Gardner
中科院分区：
文献类型：
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作者：
J. Marshall;D. Fisher;T. Gardner
断层运动学、地震活动性和横跨哥斯达黎加中部的大地测量数据揭示了一个扩散的断层带，这里称为中央哥斯达黎加变形带（CCRDB）。CCRDB确定了巴拿马地块的西缘，并将沿着加勒比海岸的北巴拿马变形带（NPDB）与沿沿着太平洋海岸的中美洲海沟（MAT）连接起来。CCRDB和MAT的交界处与俯冲科科斯板块上从光滑到粗糙地壳的突然过渡（粗糙-光滑边界）相吻合。与科科斯海岭相关的粗糙增厚的洋壳的浅俯冲将活动缩短转移到CCRDB断层沿着的火山弧中。沿这一地带的断层运动学变化沿着可能反映了三种变形机制：洋脊凹陷引起的水平缩短和剪切、浅俯冲引起的基底牵引和俯冲海山粗糙度引起的局部块体隆起。在弧前（区域1）内，中尺度断层表现出扭张，其中陡峭的NE向区域尺度断层与太平洋海岸相交。在火山弧（域2），中尺度断裂主要表现为左旋和右旋滑动的NE和NW走向的共轭断层，分别。在弧后（域3）接近NPDB，平移断层被平移挤压和地壳增厚所改变。断层运动学与地震震源机制和全球定位系统（GPS）测量结果一致。放射性年龄的限制证实，断层晚于晚第三纪开始的浅俯冲。随之而来的变形前锋已经向北传播到火山弧，沿着地震活跃的CCRDB到它现在的位置。在弧前，浅俯冲的影响被与下冲海山有关的局部隆起所覆盖。
Fault kinematics, seismicity, and geodetic data across central Costa Rica reveal a diffuse fault zone, here named the Central Costa Rica Deformed Belt (CCRDB). The CCRDB defines the western margin of the Panama block and links the North Panama Deformed Belt (NPDB) along the Caribbean coast with the Middle America Trench (MAT) along the Pacific coast. The junction of the CCRDB and the MAT coincides with an abrupt transition from smooth to rough crust on the subducting Cocos plate (rough‐smooth boundary). Shallow subduction of rough, thickened oceanic crust associated with the Cocos Ridge shifts active shortening into the volcanic arc along faults of the CCRDB. Variable fault kinematics along this zone may reflect three combined deformation mechanisms: horizontal shortening and shear from oceanic ridge indentation, basal traction from shallow subduction, and localized block uplift from subducting seamount roughness. Within the forearc (domain 1), mesoscale faults express transtension where steep NE striking regional‐scale faults intersect the Pacific coast. Across the volcanic arc (domain 2), mesoscale faults exhibit mostly sinistral and dextral slip on NE and NW striking conjugate faults, respectively. Approaching the NPDB in the back arc (domain 3), transcurrent faulting is modified by transpression and crustal thickening. Fault kinematics are consistent with earthquake focal mechanisms and Global Positioning System (GPS) measurements. Radiometric age constraints confirm that faulting postdates the late Neogene onset of shallow subduction. The ensuing deformation front has propagated northward into the volcanic arc to its present position along the seismically active CCRDB. Within the forearc, the effect of shallow subduction is overprinted by local uplift related to underthrusting seamounts.