The geological structures buried in the Mexicali Valley need to be better constrained. The Calipatria Fault is an essential key as it could represent an old strand of the San Andreas Fault system. Previous and two new seismic profiles in the Mexicali Valley and Altar Desert have been processed and interpreted. Chaotic and Low Amplitude Seismic Anomalies (CLASA) observed in the seismic profiles have revealed the Calipatria Deformation Zone, showing a high correlation with gravity maxima. This correlation could extend to the Salton Sea, resulting in an ancient plate boundary connected to the Southern San Andreas Fault. We propose that this deformation zone is a transtension region due to the change from an orthogonal rifting to an oblique rifting similar to the observations on analog models based on the northern Gulf of California. This change in the rifting style produced narrow basins that facilitated continental breakup observed on magnetic anomalies and deep wells penetrating igneous rocks.

中文翻译：

---

墨西卡利山谷二维地震剖面显示的卡利帕特里亚变形带。古代板块边界的证据？


墨西卡利山谷中埋藏的地质结构需要得到更好的约束。卡利帕特里亚断层是一个重要的关键，因为它可能代表圣安德烈亚斯断层系统的一条旧线。墨西卡利山谷和阿尔塔沙漠的先前和两个新的地震剖面已得到处理和解释。在地震剖面中观察到的混沌低振幅地震异常（CLASA）揭示了卡利帕特里亚变形带，显示出与重力最大值的高度相关性。这种相关性可能会延伸到索尔顿海，从而形成与南圣安德烈亚斯断层相连的古老板块边界。我们认为，该变形区是由于从正交裂谷到倾斜裂谷的变化而形成的转变区域，类似于基于加利福尼亚湾北部的模拟模型的观测结果。裂谷类型的这种变化产生了狭窄的盆地，促进了在磁异常和穿透火成岩的深井上观察到的大陆分裂。