The 45 km-long, north-trending East Franklin Mountains Fault lies in the southern Rio Grande rift (Texas). Late Quaternary normal fault scarps up to 20 m high traverse the eastern range front, but also bulge up to 2 km out onto the piedmont in lobes as much as 3.5 km wide. In the lobe areas the range-front fault strand displays no fault scarps, as if displacement has shifted to the piedmont strand since ca. 400 ka. We divide the faulted piedmont alluvial fans into seven age classes (from Middle Pleistocene to Holocene), based on erosional dissection and soil profile development. Piedmont scarps in Qf1 deposits (250–400 ka) range from 18 to 20 m high; in Qf2-3 deposits (65–100 ka), 9–10 m high; and in Qf3-4 deposits (20 ka), 2.7–4 m high (the latest displacement event). Scarp heights underestimate true vertical displacement of the footwall surface, which lies buried beneath younger fan deposits of unknown thickness on the hanging wall. Hanging-wall aggradation also causes variable scarp heights along strike on single-age landforms, with burial thickness a second-degree polynomial function (parabolic) of distance to the nearest active stream. Our paleoseismic trench on a 9.8 m-high scarp exposed evidence for five displacement events in the past 44 ka, the latest three of which had vertical displacements of 3–4 m. Such displacements imply surface ruptures longer than the 26.5 km fault length previously mapped in the USA, indicating rupture extended onto adjacent faults. The minimum long-term slip rate (>11.2 m in 44 ka) is 0.25 mm/yr; over last full seismic cycle (ca. 11–29 ka) it is 0.20–0.21 mm/yr. Optically-stimulated luminescence (OSL) dating shows that fine sand-silt grains in colluvial deposits were not all zeroed during deposition. Single-aliquot dating of quartz grains yielded multiple OSL age peaks, the youngest peaks of which yield a chronology compatible with stratigraphy and soil development in the colluvial wedge sequence.

45 公里长、北向的东富兰克林山脉断层位于格兰德河裂谷南部（德克萨斯州）。高达 20 m 高的晚第四纪正断层陡坎穿过东部山脉前缘，但也以 3.5 公里宽的裂片向山麓突出达 2 公里。在叶瓣区域，山脉前断层链没有显示断层陡峭，好像自大约 20 年以来位移已经转移到山麓链。400 卡。我们根据侵蚀解剖和土壤剖面发育将断层山麓冲积扇分为七个年龄等级（从中更新世到全新世）。Qf1 矿床 (250-400 ka) 中的山麓陡坡高 18 至 20 m；在 Qf2-3 矿床中（65-100 ka），高 9-10 m；在 Qf3-4 矿床（20 ka）中，高 2.7-4 m（最近的位移事件）。陡坡高度低估了下盘面的真实垂直位移，它埋在悬壁上厚度未知的较年轻的扇形沉积物之下。悬壁加成还导致沿单一时代地貌走向的陡坡高度发生变化，埋藏厚度是到最近的活动河流距离的二次多项式函数（抛物线）。我们在 9.8 m 高陡坡上的古地震海沟暴露了过去 44 ka 中五个位移事件的证据，其中最近的三个具有 3-4 m 的垂直位移。这种位移意味着地表破裂比之前在美国绘制的 26.5 公里断层长度更长，表明破裂扩展到相邻断层。最小长期滑移率（在 44 ka 中 >11.2 m）为 0.25 mm/yr；在上一个完整的地震周期（大约 11-29 ka）中，它是 0.20-0.21 毫米/年。光激发光 (OSL) 测年表明，崩积沉积物中的细砂粉砂颗粒在沉积过程中并未全部归零。石英颗粒的单等分测年产生了多个 OSL 年龄峰，其中最年轻的峰产生的年代学与崩积楔序列中的地层和土壤发育相一致。