4:15 PM - 4:30 PM
[SSS14-22] Surface ruptures in Dongli and Fuli area of the September 18¸ 2022¸ Chihshang earthquake¸ Eastern Taiwan
Keywords:Longitudinal Valley Fault, Central Range Fault, Eastern Taiwan
Two shallow crustal earthquakes, Mw 6.4 and Mw 6.9¸ occurred on September 17 and 18¸ 2022¸ as a foreshock and a mainshock at Guanshan and Chihshang in the southern Longitudinal Valley (LV) in eastern Taiwan. The LV is located in the Eurasian ـ Philippine Sea plate boundary near the eastern margin of Taiwan. At the latitude of the 2022 seismic sequence, the plate boundary is defined by a conjugate fault system that includes the causative west dipping Central Range Fault (CRF)¸ and east dipping Longitudinal Valley Fault (LVF).
A field reconnaissance was conducted from October 18 to 22¸ 2022 by a team of researchers from the Geotechnical Extreme Events Reconnaissance (GEER) Association, the National Center for Research on Earthquake Engineering (NCREE)¸ and National Chi Nan University (NCNU). The reconnaissance teams investigated bridge and building failure, ground failure¸ and surface fault rupture in the damage area.
The surface fault rupture reconnaissance focused on damage in the towns of Fuli and Dongli¸ located along the LVF and near the epicenters. In Fuli¸ surface rupture was observed by surface investigation and aerial drone survey along the LVF on Yong-An street with lengths up to 900 m and widths up to 50m. The total displacement of fault rupture in Fuli moved approximately to 90 cm left-lateral and 5 cm of upـtoـthe-southeast vertical direction. In Dongli, most ruptures were observed near Dongli Junior High school. From field investigation and aerial drone survey¸ three clearly delineated fault zones were observed with lengths up to 560 m and widths up to 164 m. Individual vertical separations ranged from a few centimeters up to 20 cm¸ indicating a predominance of shortening and uplift as opposed to predominantly sinistral displacement in Fuli.
Two 3D schematic fault models from observed displacement features in Fuli and Dongli illustrate two unique styles of complex deformation behaviors along LVF. Additionally, surface ruptures associated with the September 2022 sequence are notably similar to surface ruptures documented during the 1951 earthquake sequence¸ the 2003 Chengkung earthquake¸ and the March¸ 2022 Changbin earthquake along the LVF.
A field reconnaissance was conducted from October 18 to 22¸ 2022 by a team of researchers from the Geotechnical Extreme Events Reconnaissance (GEER) Association, the National Center for Research on Earthquake Engineering (NCREE)¸ and National Chi Nan University (NCNU). The reconnaissance teams investigated bridge and building failure, ground failure¸ and surface fault rupture in the damage area.
The surface fault rupture reconnaissance focused on damage in the towns of Fuli and Dongli¸ located along the LVF and near the epicenters. In Fuli¸ surface rupture was observed by surface investigation and aerial drone survey along the LVF on Yong-An street with lengths up to 900 m and widths up to 50m. The total displacement of fault rupture in Fuli moved approximately to 90 cm left-lateral and 5 cm of upـtoـthe-southeast vertical direction. In Dongli, most ruptures were observed near Dongli Junior High school. From field investigation and aerial drone survey¸ three clearly delineated fault zones were observed with lengths up to 560 m and widths up to 164 m. Individual vertical separations ranged from a few centimeters up to 20 cm¸ indicating a predominance of shortening and uplift as opposed to predominantly sinistral displacement in Fuli.
Two 3D schematic fault models from observed displacement features in Fuli and Dongli illustrate two unique styles of complex deformation behaviors along LVF. Additionally, surface ruptures associated with the September 2022 sequence are notably similar to surface ruptures documented during the 1951 earthquake sequence¸ the 2003 Chengkung earthquake¸ and the March¸ 2022 Changbin earthquake along the LVF.