The Salton Trough is one of the few regions on Earth where rifting is subaerial instead of submarine. We use the relative attenuation of teleseismic P phases recorded by the Salton Trough Seismic Imaging Project to investigate lithospheric and asthenospheric structures that form during extension. Map‐view analysis reveals stronger attenuation within the Salton Trough than in the adjacent provinces. We then construct tomographic models for variations in seismic attenuation with depth to discriminate between crustal and mantle signals with a damped least squares approach and a Bayesian approach. Synthetic tests show that models from damped least squares significantly underestimate the strength of attenuation and cannot separate crustal and mantle signals even if the tomographic models are allowed to be discontinuous at the lithosphere‐asthenosphere boundary (LAB). We show that a Bayesian approach overcomes these problems when inverting the same synthetic data sets and that shallow and deep signals are more clearly separated when imposing a discontinuity. With greater than 95% confidence, the results reveal first, that attenuation occurs primarily beneath the LAB; second, that the width of the attenuative region is narrower than the rift at 120 km depth; and third, that the strength of attenuation requires that the attenuative feature represents a melting‐column similar to those beneath mid‐ocean ridges. The narrow width of the melting column below the volatile‐free solidus is inconsistent with models for passive upwelling, where flow is driven only by rifting. Instead, we attribute the generation of incipient oceanic crust to mantle upwelling focused by buoyancy into a narrow diapir.

中文翻译：

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地震衰减层析成像成像在索尔顿海槽下的动态上升

索尔顿海槽是地球上为数不多的，不是空中而是地下的裂谷区域之一。我们使用Salton槽地震成像项目记录的远震P相的相对衰减来研究伸展过程中形成的岩石圈和软流圈结构。地图视图分析显示，萨尔顿海槽内的衰减比相邻省份更大。然后，我们构建层析成像模型，以利用深度最小二乘法和贝叶斯方法区分地震衰减随深度的变化，以区分地壳和地幔信号。综合测试表明，即使最小化层析成像模型在岩石圈-软流圈边界（LAB）上的不连续性，阻尼最小二乘法的模型也大大低估了衰减的强度，并且无法分离地壳和地幔信号。我们表明，当反转相同的合成数据集时，贝叶斯方法克服了这些问题，并且在施加不连续性时，浅信号和深信号被更清楚地分离。结果具有95％的置信度，首先表明，衰减主要发生在LAB以下。第二，衰减区域的宽度比深度为120 km的裂谷窄。第三，衰减的强度要求衰减特征代表的融化柱类似于洋中脊下方的柱。无挥发固相线以下的熔融塔狭窄宽度与被动上升流模型（其仅通过裂谷驱动流动）不一致。相反，我们将新生洋壳的产生归因于以浮力为中心的地幔上升流进入狭窄的底辟。