Evidence for prehistoric coseismic folding along the Tsaotun segment of the Chelungpu fault near Nan‐Tou, Taiwan

Abstract

[1] Taiwan's 1999 M w 7.6 earthquake generated over 85 km surface rupture along the Chelungpu thrust fault. Paleoseismic studies at the Shi-Jia site near Nantou city, reveal folding as the predominant form of deformation. Stratigraphic relations across the 1999 fold scarp show the style and degree of deformation caused by the penultimate event is similar to observed 1999 deformation. A boring transect across the fold scarp provides additional evidence of an earlier earthquake. Investigations at the Shi-Jia site revealed three prehistoric events; accelerator mass spectrometry (AMS) radiocarbon ages indicate that the penultimate earthquake occurred between 1160 and 1440 A.D. Paleoseismic studies north of the Shi-Jia site reveal much younger penultimate earthquakes, suggesting a 1999-type event may not be characteristic along the Tsaotun segment of the Chelungpu fault.

Spatio-temporal Slip, and Stress Level on the Faults within the Western Foothills of Taiwan: Implications for Fault Frictional Properties

“…No earthquake as large as the Chi-Chi earthquake is known to have occurred in the area over the last few centuries. Paleoseismic investigations have revealed prehistorical ruptures with slip similar to those observed in 1999 at a few sites, however, it seems clear that these paleoseismic events occurred at different times and at different places (CHEN et al, 2004LEE et al, 2001a;STREIG et al, 2007). Clearly, the Chelungpu fault does not act with the repetition of a characteristic earthquake similar to the Chi-Chi event.…”

“…The longest record of paleoseismic investigations, which was carried at Chushan on the southern segment of the Chelungpu fault, has revealed five different events with slip similar to that observed in 1999 over the last 2000 years. Similarly, at Shi-Jia site, three events occurred over the last 1200 years (STREIG et al, 2007). Thus the return period of large events on the Chelungpu fault seems to conflict with estimates derived from the long term slip rate and the pattern of interseismic locking.…”

Pleistocene alluvial deposits dating along frontal thrust of Changhua Fault in western Taiwan: The cosmic ray exposure point of view

“…In addition, the highly dynamic conditions of fluvial deposition enhance the probability for material recycling, particularly from one terrace to another. Nevertheless, the radiocarbon technique has been applied successfully to date geomorphic features in Taiwan, bringing Holocene to the early Pleistocene temporal constraints for studies of volcanic events (Chen et al, 2010a,b;Belousova et al, 2010), active tectonics (Liew et al, 1993;Vita-Finzi, 2000;Lee et al, 2001;Chen et al, 2001Chen et al, , 2003aChen et al, ,b, 2009Streig et al, 2007;Hsieh and Rau, 2009;Yen et al, 2009) as well as gravitational collapse events (Hsieh and Chyi, 2010), alluvial (Hsieh and Knuepfer, 2001;Ota et al, 2002) and marine terraces (Yamaguchi and Ota, 2001;Hsieh et al, 2006). The time range of radiocarbon dating being limited at best to the last 45 kyr, terraces older than that have been dated using approaches, such as luminescence-based techniques (Wintle and Murray, 2006;Wintle, 2008;Preusser et al, 2009).…”

Characteristics of Coseismic Thrust-Related Folding from Paleoseismic Investigation Responsible for the 1999 Chi-Chi Earthquake of Central Taiwan

“…Over the past ten years, we have excavated numerous sites and continuously cored borings on the Chelungpu fault, where the surface rupture shows surface deformation within the Holocene deposits; our results have provided quantitative data for late Holocene slip rates ( Fig. 1; Chen et al, 2001aChen et al, , b, 2004Chen et al, , 2007aOta et al, 2001Ota et al, , 2005Streig et al, 2007). Bedrock exposed along the Shihkang fault has not been characterized in previous paleoseismic studies.…”

“…Active thrust faults commonly show complex geometric patterns of faulting and folding in response to different sedimentary facies, thickness, and lithologic characters of Holocene deposits. Previous studies along the Chi-Chi earthquake rupture have shown that fault-tip deformation can be subdivided into breakthrough thrust and blind-thrust components (Chen et al, 2001a(Chen et al, , b, 2004(Chen et al, , 2007aOta et al, 2001Ota et al, , 2005Streig et al, 2007). We will integrate these excavated profiles across the earthquake rupture to delineate the characteristics of thrust-related fold and to reconstruct the growth history of the fault tip fold.…”