Abstract A three-dimensional P and S-wave travel-time tomography, as well as Vp/Vs ratio images, were obtained for the southernmost tip of the Baja California Peninsula in Mexico. The area analyzed include Los Cabos block and part of the Gulf coast. The tomography obtained reveals in detail the heterogeneities of the crustal seismic velocity structure of the Los Cabos block. Results show an overall low velocity structure for both P- and S-waves under the Baja California peninsula down to a depth of ~25 km around the peninsular axis, particularly under Sierra La Laguna and near the Gulf of California (GoC) coast. Low P- and S-wave velocities are also present under the Gulf near the coast whereas fast velocities are observed under the Gulf away from the shoreline. Low and high Vp/Vs ratios are observed to alternate throughout the study area. The low seismic velocities may be explained because the crust in Los Cabos block is highly fractured and fluid-saturated, and has a high heat flux which is manifested as geothermal activity (e.g. hot springs observed all along the block). These low body wave velocities coincide with the existence of an asthenospheric mantle sandwiched by the continental crust of the Los Cabos block and a stalled subducted slab reported by Di Luccio et al. (2014). This mantle strip may be chemically depleted or dry inhibiting the development of active post-subduction volcanism.

中文翻译：

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下加利福尼亚半岛最南端的 3D 旅行时断层扫描

摘要 获得了墨西哥下加利福尼亚半岛最南端的三维 P 波和 S 波走时断层扫描以及 Vp/Vs 比图像。分析的区域包括洛斯卡沃斯区块和墨西哥湾沿岸的部分地区。获得的层析成像详细揭示了洛斯卡沃斯地块地壳地震速度结构的非均质性。结果显示，下加利福尼亚半岛下的 P 波和 S 波的整体低速结构在半岛轴周围深度约 25 公里，特别是在 Sierra La Laguna 下和加利福尼亚湾 (GoC) 海岸附近。在靠近海岸的海湾下方也存在低 P 波和 S 波速度，而在远离海岸线的海湾下方观察到快速速度。观察到低和高 Vp/Vs 比率在整个研究区域交替出现。低地震速度可能是因为洛斯卡沃斯地块的地壳高度破裂和流体饱和，具有高热通量，表现为地热活动（例如沿地块观察到的温泉）。这些低体波速度与夹在洛斯卡沃斯地块大陆地壳之间的软流圈地幔和迪卢乔等人报道的停滞的俯冲板块的存在相吻合。(2014)。这个地幔带可能在化学上已耗尽或干燥，从而抑制了活跃的俯冲后火山活动的发展。这些低体波速度与夹在洛斯卡沃斯地块大陆地壳之间的软流圈地幔和迪卢乔等人报道的停滞的俯冲板块的存在相吻合。(2014)。这个地幔带可能在化学上已耗尽或干燥，从而抑制了活跃的俯冲后火山活动的发展。这些低体波速度与夹在洛斯卡沃斯地块大陆地壳之间的软流圈地幔和迪卢乔等人报道的停滞的俯冲板块的存在相吻合。(2014)。这个地幔带可能化学耗尽或干燥，从而抑制了活跃的俯冲后火山活动的发展。