Reevaluation of surface rupture parameters and faulting segmentation of the 2001 Kunlunshan earthquake (Mw7.8), northern Tibetan Plateau, China

摘要

The 14 November 2001, M w = 7.8 Kunlunshan earthquake ruptured the westernmost part of the Kunlun Fault, northern Tibetan Plateau. The main segment affected by this event was the Kusaihu segment. Field investigations allowed us to constrain the length, the width, and the coseismic horizontal displacement distribution of the Kunlunshan earthquake rupture zone. The mapped surface rupture zone starts from 90.257°E in the west and ends at 94.795°E in the east with a total length of 426 km. It consists of three main sections, the western strike-slip section, the transtensional section, and the eastern strike-slip section. The rupture zone is oriented N100° ± 10°E on average. The distribution of the coseismic horizontal displacements is characterized by multiple peaks departing clearly from a general bell-shaped distribution. Reassessment of the maximum coseismic horizontal left-lateral displacement yields a value of 7.6 ± 0.4 m at the site (35.767°N, 93.323°E) consistent with independent measurements derived from interferometric synthetic aperture radar and seismology. From this site the horizontal displacement decreases unevenly to both the west and east. Coseismic vertical (reverse) displacement is also noted at the eastern end of the rupture but it remains much smaller than the horizontal component. The width of the rupture zone varies from site to site from several meters to few kilometers. The maximum width measured reaches 8 km along the Yuxi Feng subsection where a large number of shaking related cracks were well developed.