The continental part of west‐central Mexico is characterized by the active extensional tectonic regimes of the Trans‐Mexican volcanic belt and the adjacent southern Basin and Range Province. The deformation of the latter is distributed over several topographically very pronounced grabens and half‐grabens (width 10–20 km, length ≤200 km⁠; throw 1–2 km), including the Aguascalientes, Juchipila, Tlaltenango, and Bolaños grabens. Here, an A.D. 1774–1775 earthquake series in that area is documented based on numerous contemporary sources. The 6 November 1774 mainshock caused moderate‐to‐severe damage in several communities of the Bolaños graben, including the silver mining town of Bolaños, and moderate damage to communities in the Tlaltenango graben, such as the administrative center of Colotlán. Based on the macroseismic intensity distribution, the epicenter was in the Bolaños graben. The preferred magnitude of the mainshock is ∼6.0±0.5⁠. No major historical earthquake had been reported previously from this region. Existing ground‐shaking hazard models may, therefore, give a false sense of security.In the Bolaños graben, motion along the graben‐bounding faults and the observed tilting of the graben shoulders has to be mostly younger than the 19.9 Ma age of the youngest basalt of the graben‐shoulder stratigraphy. Its correlation across the western master fault indicates a 1300 m throw and a vertical long‐term slip rate of 0.07 mm/yr⁠. The observations of alluvial fan deposits juxtaposed against the footwall ignimbrites along the western master fault of the Bolaños graben, the displacement of alluvial fan deposits along secondary faults within the graben, and the existence of hot springs along the western boundary fault all are indicative of active deformation, and so is evidently the A.D. 1774 earthquake.

中文翻译：

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1774年11月6日，MI 6BolañosGraben地震（墨西哥西部中部南部盆地和山脉省）：宏观地震观测和新构造意义

墨西哥中西部的大陆地区以跨墨西哥火山带及邻近的南部盆地和兰治省的活跃伸展构造为特征。后者的变形分布在几个地形非常明显的grab和半and（宽10–20 km，长≤200km⁠；投掷1-2 km）上，包括阿瓜斯卡连特斯山脉，朱奇比拉，Tlaltenango和博拉尼奥斯grab。在此，根据众多现代文献记录了该地区的1774–1775年地震序列。1774年11月6日的主震对博拉尼奥斯抓地的几个社区（包括白银开采镇博拉尼奥斯）造成了中度至重度破坏，而对Tlaltenango抓地中的社区（如科洛特兰行政中心）造成了中度至重度破坏。根据宏观地震烈度分布，震中位于博拉尼奥斯（Bolaños）地grab。主震的最佳震级约为6.0±0.5⁠。此前，该地区未曾发生过重大的历史地震。因此，现有的震动危险模型可能会给人一种错误的安全感：在Bolañosen陷中，沿着grab陷边界断层的运动以及所观察到的grab陷肩部的倾斜都必须比年龄最小的19.9 Ma大得多。 en肩地层的玄武岩。整个西部主断层的相关性表明，该断层距地面1300 m，垂直长期滑动速率为0.07 mm / yr。冲积扇沉积物沿着波拉尼奥斯grab片的西部主断裂并排在底盘火成岩上，沿冲积岩中次生断裂的冲积扇沉积物位移，