• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Pure and Applied Geophysics >Structural and Seismic Stratigrapic study in the Center of the Magdalena Shelf in the Western Margin of Baja California Based on Seismic Reflection Data
【24h】

Structural and Seismic Stratigrapic study in the Center of the Magdalena Shelf in the Western Margin of Baja California Based on Seismic Reflection Data

机译：基于地震反射数据的下加利福尼亚州西缘马格达莱纳书架中心的结构和地震地层学研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The Magdalena Shelf is a shallow, low-relief surface located along the Baja California Pacific margin. As part of a forearc basin, the shelf was a convergent margin setting before the oblique divergent plate boundary formed in the Gulf of California at 12 Ma. It is thought that since 12-8 Ma, this basin has been a transtensional or strike-slip basin. To constrain the geometry, structural characteristics and some stratigraphic relationships, an active-source, seismic-reflection study was carried out in the central part of the shelf. As a result, the analyzed data show faults, basins and unconformities. Two out of four observed basins are clearly controlled by the Santa Margarita and San Lazaro faults that dip similar to 40A degrees NE; a third basin is controlled by the Tosco-Abreojos fault. These three basins are part of the deformation zone that is associated with the Tosco-Abreojos fault system. The Iray-Margarita basin, on the other hand, is a fourth basin located at the northeast sector of the study area. An additional feature observed is a stepover lying between the overlapping ends of the Santa Margarita and San Lazaro faults. Small faults oriented sub-parallel to the above major faults are present, mainly throughout the western sector of the study area. Some of those minor faults cut through the seafloor indicating recent tectonic activity. Santa Margarita, San Lazaro and Tosco-Abreojos are also the names given to half-grabens controlled by the active faults that have the same names. The first two basins are affected by many more small faults in comparison with what we see in the third basin. Tectonically, this means that those two basins are the more active in the area of study. In all four basins, the upper seismic sequence consists of sediments controlled by faults of Neogene age. We found that the Iray-Santa Margarita basin is the deepest of all four basins (beyond the resolution of the data, > 5 km), and lack of minor faults there indicates that the basin is not tectonically active. Two unconformities are present in the region, unconformity-1 of Miocene age and unconformity-2 of Paleocene-Eocene and Cretaceous ages. Unconformity-1 is present in the entire region, while Unconformity-2 is present mainly in the Iray-Magdalena and San Lazaro basins. In the Iray-Magdalena basin the sedimentary sequences show an uplift that took place in late Jurassic time along its western portion. We also see that moderate compressive deformation increases gradually from west to east. A chaotic-reflector oriented NW-SE is observed with an irregular shape in all regions. It shows very superficial in some places, sub-parallel to the major faults and in association with the subduction complex. Seismic activity reported for the region showed a strong correlation with the fault plane of the Santa Margarita fault, indicating that the Tosco-Abreojos deformation zone is similar to 90 km wide in the area. Finally, the Santa Margarita fault should be considered in future hazard-risk assessments because of their proximity to Puerto San Carlos. As it has been reported, local seismic events (M < 4) have generated alarm in the local populace, as well as soil liquefaction and minor damage to structures in the region.
机译：玛格达莱纳书架（Magdalena Shelf）是一个浅浅的浮雕表面，位于下加利福尼亚太平洋边缘。作为前臂盆地的一部分，该架子在12 Ma处在加利福尼亚湾形成的倾斜发散板块边界之前是一个收敛的边缘位置。认为自12-8 Ma以来，该盆地一直是张拉或走滑盆地。为了限制几何形状，结构特征和某些地层关系，在架子的中央进行了有源震源反射研究。结果，分析数据显示出断层，盆地和不整合面。四个观测盆地中有两个明显受到圣玛格丽塔和圣拉萨罗断层的控制，这些断层的倾角接近东北40A。第三盆地由Tosco-Abreojos断层控制。这三个盆地是与Tosco-Abreojos断层系统有关的变形带的一部分。另一方面，Iray-Margarita盆地是位于研究区域东北部的第四个盆地。观察到的另一个特征是在圣玛格丽塔断层和圣拉萨罗断层的重叠端之间存在一个过渡。存在与上述主要断层次平行的小断层，主要分布在整个研究区的西部地区。这些较小的断层中的一些穿过海底，表明最近的构造活动。圣玛格丽塔（Santa Margarita），圣拉萨罗（San Lazaro）和托斯科-阿布雷欧霍斯（Tosco-Abreojos）也是由活动断层控制的同名半透明岩层的名称。与第三个盆地相比，前两个盆地受更多的小断层影响。从构造上讲，这意味着这两个盆地在研究领域中更为活跃。在所有四个盆地中，上部地震序列由受新近纪时代断层控制的沉积物组成。我们发现Iray-Santa Margarita盆地是所有四个盆地中最深的（超出数据分辨率，> 5 km），并且那里没有小断层表明该盆地没有构造活动。该地区存在两种不整合面，中新世时代的不整合面1和古新世-始新世和白垩纪的不整合面2。整个区域都存在不整合面1，而主要在Iray-Magdalena和San Lazaro盆地中存在不整合面2。在伊赖－马格达莱纳盆地，沉积序列显示出侏罗纪晚期沿其西部发生的隆升。我们还看到，适度的压缩变形从西向东逐渐增加。观察到在所有区域中均以不规则形状观察到取向为混沌反射器的NW-SE。它在某些地方表现得非常肤浅，与主要断层平行并且与俯冲复合体有关。该地区报道的地震活动与圣玛格丽塔断层的断层面密切相关，这表明该地区的Tosco-Abreojos变形带宽约90 km。最后，由于圣玛格丽塔断裂靠近圣卡洛斯港，因此应在未来的风险评估中考虑。据报道，当地地震事件（M <4）已在当地民众中引起警报，以及土壤液化和对该区域结构的轻微破坏。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号