Large earthquakes often do not occur on a simple planar fault but involve rupture of multiple geometrically complex faults. The 2016 M_w 7.8 Kaikoura earthquake, New Zealand, involved the rupture of at least 21 faults, propagating from southwest to northeast for about 180 km. Here we combine space geodesy and seismology techniques to study subsurface fault geometry, slip distribution, and the kinematics of the rupture. Our finite‐fault slip model indicates that the fault motion changes from predominantly right‐lateral slip near the epicenter to transpressional slip in the northeast with a maximum coseismic surface displacement of about 10 m near the intersection between the Kekerengu and Papatea faults. Teleseismic back projection imaging shows that rupture speed was overall slow (1.4 km/s) but faster on individual fault segments (approximately 2 km/s) and that the conjugate, oblique‐reverse, north striking faults released the largest high‐frequency energy. We show that the linking Conway‐Charwell faults aided in propagation of rupture across the step over from the Humps fault zone to the Hope fault. Fault slip cascaded along the Jordan Thrust, Kekerengu, and Needles faults, causing stress perturbations that activated two major conjugate faults, the Hundalee and Papatea faults. Our results shed important light on the study of earthquakes and seismic hazard evaluation in geometrically complex fault systems.

Online Material: Figures of station deployment time and of spatial and temporal depiction of aftershocks, and tables of station information and aftershock catalogs. At 08:02 (local and Beijing time) on 20 April 2013, an earthquake of M s 7.0 ( M w 6.6) struck Lushan County in Sichuan Province, southwestern China (hereafter referred to as the Lushan earthquake). The Lushan earthquake resulted in casualties and severe damage to the buildings and to the economic activities of the region. The earthquake left 193 dead, up to 10,000 injured, and 25 missing. The direct economic loss hit over $1.6 billion U.S. The Lushan earthquake is the second destructive earthquake to have occurred in the southern segment of the Longmenshan fault zone since the 12 May 2008 M s 8.0 Wenchuan earthquake (Fig. 1). The distance between the epicenters of the Lushan earthquake and the Wenchuan earthquake is about 87 km (Fang, Wu, Wang, Lü, et al. , 2013). As happened following the Wenchuan earthquake, the occurrence of the Lushan earthquake also stimulated lots of discussions on the seismic risk potential and prediction in southwest China. In particular, whether it was a large aftershock of the Wenchuan earthquake has been heatedly debated (Chen et al. , 2013; Du et al. , 2013; J. Liu et al. , 2013; Wang et al. , 2013; Jia et al. , 2014). Figure 1. (a) Tectonic settings of the Longmenshan fault zone. Red and yellow stars indicate the epicenters of the Wenchuan and Lushan earthquakes, respectively. The focal mechanisms of the Lushan earthquake and Wenchuan earthquake are also shown. Red circles represent aftershocks of the Lushan and Wenchuan earthquakes. Black lines indicate the main faults. The inset map shows the location of the study region in the Chinese mainland. (b) The distribution of seismic stations in and around the epicentral region of the Lushan …