- © 2014 by the Seismological Society of America
Online Material: Supplemental seismic reflection data and interpretations; figures of seismicity; table of fault area versus moment magnitude.
Recent destructive earthquakes, such as the 2008 Mw 7.9 Wenchuan, China, event, have demonstrated the complex nature of thrust‐fault ruptures, which commonly involve slip along multiple‐fault splays and breach lateral segment boundaries (e.g., Yeats et al., 1997; Hubbard and Shaw, 2009; Hubbard et al., 2010; Li, Jia, et al., 2010). These characteristics pose significant challenges when assessing the seismic hazards of active thrust faults. In many regions of active faulting, earthquake forecasts rely primarily on surface ruptures to define previous fault activity, slip rates, and paleoearthquake magnitudes. As a result, assessments of past and future event magnitudes are often based on the lengths of surface‐fault traces, with large offsets between surface traces being used to define the limits of rupture patches (e.g., Magistrale and Day, 1999; Zhang et al., 1999; Wesnousky, 2006, 2008). However, many active thrust sheets consist of multiple faults that merge or interact at depth (e.g., Shaw et al., 2002; Yue et al., 2005; Plesch et al., 2007; Hubbard et al., 2010). These fault networks pose significant seismic hazards as they have the potential to produce large, multisegment earthquakes.
This study examines the subsurface geometry of a highly segmented thrust system in the southern Junggar basin, northwest China, which generated the 1906 Mw 7.4–8.2 Manas, China, earthquake (Avouac et al., 1993; Burchfiel et al., 1999; Wang et al., 2004). This rupture has been interpreted to breach surface‐trace offsets of 5–10 km (e.g., Avouac et al., 1993). Using high‐quality 2D and 3D seismic reflection surveys, seismicity, and surface geology, we develop a 3D model of the faults that sourced this large magnitude rupture in order to investigate the …