Delineation of Faulting and Basin Geometry along a Seismic Reflection Transect in Urbanized San Bernardino Valley, California
Delineation of Faulting and Basin Geometry along a Seismic Reflection Transect in Urbanized San Bernardino Valley, California
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加利福尼亚州城市化圣贝纳迪诺谷沿地震反射断面的断层和盆地几何形状的描绘
DOI：
10.1785/0120010222
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发表时间：
2002
影响因子：
3
通讯作者：
M. Anderson
中科院分区：
文献类型：
--
作者：
W. Stephenson;J. Odum;Robert A. Williams;M. Anderson
通过加利福尼亚州圣贝纳迪诺山谷获得的14公里连续浅层地震反射数据揭示了圣哈辛托和圣安德烈亚斯断层之间的许多断层以及复杂的下降和隆起地块模式。这些数据还表明，洛马林达断层继续向东北方向延伸至少4.5公里，超过其在山谷南缘的最后一张地图位置，并延伸到圣贝纳迪诺市中心至少2公里以内。圣哈辛托断层东北部山谷中以前未发现的断层也被成像，包括推断的班宁断层的西延和几个未命名的断层。Rialto-Colton断层解释为圣哈辛托断层西南方向。地震数据显示，结晶基底的顶部横跨70%的剖面长度，显示基底在佩里斯山和圣哈辛托断层之间的总体倾角约为西南10°。重力和航磁数据证实了圣哈辛托断层的解释位置，并更好地将地震剖面上的盆地深度限制在1.7公里深。这些数据还证实了其他断层位置和基底表面的总体倾角。在剖面位置，观测到了横跨圣哈辛托断层的至少1.2公里的基底视垂直位移。用这些数据描绘的盆地几何形状被用来产生模拟的地面运动，在0.05-1.0-HZ频带内，基岩响应上方的水平放大峰值为2-3.5，这与山谷中记录的地震数据一致。
Fourteen kilometers of continuous, shallow seismic reflection data acquired through the urbanized San Bernardino Valley, California, have revealed numerous faults between the San Jacinto and San Andreas faults as well as a complex pattern of downdropped and uplifted blocks. These data also indicate that the Loma Linda fault continues northeastward at least 4.5 km beyond its last mapped location on the southern edge of the valley and to within at least 2 km of downtown San Bernardino. Previously undetected faults within the valley northeast of the San Jacinto fault are also imaged, including the inferred western extension of the Banning fault and several unnamed faults. The Rialto-Colton fault is interpreted southwest of the San Jacinto fault. The seismic data image the top of the crystalline basement complex across 70% of the profile length and show that the basement has an overall dip of roughly 10° southwest between Perris Hill and the San Jacinto fault. Gravity and aeromagnetic data corroborate the interpreted location of the San Jacinto fault and better constrain the basin depth along the seismic profile to be as deep as 1.7 km. These data also corroborate other fault locations and the general dip of the basement surface. At least 1.2 km of apparent vertical displacement on the basement is observed across the San Jacinto fault at the profile location. The basin geometry delineated by these data was used to generate modeled ground motions that show peak horizontal amplifications of 2–3.5 above bedrock response in the 0.05- to 1.0-Hz frequency band, which is consistent with recorded earthquake data in the valley.