Low-Angle Reverse Faulting During Two Earthquakes on the Northern Part of the Chelungpu Fault, Deduced From the Fengyuan Trench, Central Taiwan

Abstract

ABSTRACT1 Yokohama National University, Yokohama, Japan Terr. Atmos. Ocean. Sci., Vol. 18, No. 1, March 2007 56 for horizontal and ca. 5 m for vertical) than those (2.7 m for horizontal and ca. 2 m for vertical) of the 1999 earthquake. The age of the penultimate earthquake at the Fengyuan site is the oldest earthquake recorded among the known penultimate penultimate events on the Chelungpu fault so far and suggests that this part of the Chelungpu fault may be a fault segment independent of the central and southern parts of the fault.

Deciphering cumulative fault slip vectors from fold scarps: Relationships between long‐term and coseismic deformations in central Western Taiwan

“…The single trench site located on the northern Chelungpu fault revealed only one paleo-earthquake that occurred 1.4-2.0 ka BP [Ota et al, 2007], a time period when surface ruptures are also documented on the southern and central parts of the fault, suggesting that a single earthquake could have ruptured the entire Chelungpu fault system, as Chi-Chi did. As mentioned by Ota et al [2007], it is likely that other paleo-earthquakes ruptured another identified, but unexcavated, active branch of the fault near the northern site. Although more intricate scenarios of earthquakes sequence are possible based on current paleoseismological data, these data do not contradict the idea that Chi-Chi could be a characteristic earthquake for the Chelungpu-Sanyi fault system.…”

“…The southern part of the fault might rupture in a different fashion, in paired earthquakes every ~700–800 years, possibly suggesting contribution from a different type of event possibly rupturing from the south. The single trench site located on the northern Chelungpu fault revealed only one paleo‐earthquake that occurred 1.4–2.0 ka BP [ Ota et al ., ], a time period when surface ruptures are also documented on the southern and central parts of the fault, suggesting that a single earthquake could have ruptured the entire Chelungpu fault system, as Chi‐Chi did. As mentioned by Ota et al .…”

“…As mentioned by Ota et al . [], it is likely that other paleo‐earthquakes ruptured another identified, but unexcavated, active branch of the fault near the northern site. Although more intricate scenarios of earthquakes sequence are possible based on current paleoseismological data, these data do not contradict the idea that Chi‐Chi could be a characteristic earthquake for the Chelungpu‐Sanyi fault system.…”