Characteristic Slip of Strong Earthquakes Along the Yishu Fault Zone in East China Evidenced by Offset Landforms

Abstract

The Yishu fault zone (YSFZ) is the most active fault in eastern China, and it is the location of an M 8.5 earthquake that occurred in 1668. However, topography and landforms in this area have been greatly altered by human activity during the previous three to four decades, which makes assessment of past earthquakes difficult. We therefore used a set of remote sensing images captured in the 1960s to evaluate the single‐event and multievent cumulative offsets of streams along the fault. The local landforms have preserved the Holocene seismic offsets well despite the moderately humid climate in which the local landforms have evolved rapidly. Geomorphic markers associated with 401 systematically dextrally offset streams were analyzed and measured. These offset markers are considered to record seismic rupture processes. Cumulative offset probability densities were analyzed according to slip distributions along various subsections of the YSFZ. Four strong paleoearthquakes in addition to the 1668 earthquake were revealed by offset density peaks within the YSFZ, a finding that differs from those of previous studies. The average offset of the 1668 event is approximately 9 m. The cumulative offsets of the other four paleoseismic events are essentially multiples of the latest event. A single event ruptured more than 200 km of discontinuous fault traces. The similarity of the previous five earthquakes implies that rupturing of the YSFZ has followed a characteristic slip model during the Holocene, with a right‐lateral slip rate of 2.2–2.6 mm/yr. We expect that the YSFZ is not due for another large earthquake for several thousand years.

A New Tectonic Model for the 1927M8.0 Gulang Earthquake on the NE Tibetan Plateau

“…In order to study the rupture characteristics and patterns there, we excavated two trenches, analyzed the latest offset characteristics of the fault, and collected radiocarbon samples on the latest faulted strata to constrain the timing of the latest event. We identified linear offset markers by visual interpretation of topographic morphology in the digital elevation models (DEMs) and color in the images (Guo, Han, Dong, et al, 2019; Jiang et al, 2017). The offset markers mainly include streams, terrace risers, and alluvial fan edges, which are all cut by the fault trace.…”

Evidence of long recurrence times and low slip rate along the 1668 Tancheng earthquake fault

“…至今存在异议, 主要有4种观点: (1) 北起莒县, 经临沂 至江苏宿迁, 长约230 km [8,36,37] ; (2) 从莒南左山至新沂 何庄, 长约120 km, 或至宿迁北长约160 km [6,38] ;…”

Effects of Earthquake Recurrence on Localization of Interseismic Deformation Around Locked Strike‐Slip Faults

“…Given its estimated ~130 km rupture length, its magnitude can be nowhere near the commonly quoted 8.5, as also pointed out by Jiang et al (2017). A slip of up to ~8 m has been inferred from limited paleoseismic studies with large uncertainties (Huang, 1993; Jiang et al, 2017). If we assume that the earthquake occurred 7 τ M ago ( τ M = 50 years) with average slip S o = 5 m and L = 5 D ( D = 15 km), we can predict deformation due to this event as seen today.…”