Seismotectonics and rupture process of theM_W 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening

Abstract

S U M M A R YThe 2011 October 23 M W 7.1 Van earthquake in eastern Turkey caused ∼600 deaths and caused widespread damage and economic loss. The seismogenic rupture was restricted to 10-25 km in depth, but aseismic surface creep, coincident with outcrop fault exposures, was observed in the hours to months after the earthquake. We combine observations from radar interferometry, seismology, geomorphology and Quaternary dating to investigate the geological slip rate and seismotectonic context of the Van earthquake, and assess the implications for continuing seismic hazard in the region. Transient post-seismic slip on the upper Van fault started immediately following the earthquake, and decayed over a period of weeks; it may not fully account for our long-term surface slip-rate estimate of ≥0.5 mm yr −1 . Post-seismic slip on the Bostaniçi splay fault initiated several days to weeks after the main shock, and we infer that it may have followed the M W 5.9 aftershock on the 9th November. The Van earthquake shows that updip segmentation can be important in arresting seismic ruptures on dip-slip faults. Two large, shallow aftershocks show that the upper 10 km of crust can sustain significant earthquakes, and significant slip is observed to have reached the surface in the late Quaternary, so there may be a continuing seismic hazard from the upper Van fault and the associated splay. The wavelength of folding in the hanging wall of the Van fault is dominated by the structure in the upper 10 km of the crust, masking the effect of deeper seismogenic structures. Thus, models of subsurface faulting based solely on surface folding and faulting in regions of reverse faulting may underestimate the full depth extent of seismogenic structures in the region. In measuring the cumulative post-seismic offsets to anthropogenic structures, we show that Structure-from-Motion can be rapidly deployed to create snapshots of postseismic displacement. We also demonstrate the utility of declassified Corona mission imagery (1960s-1970s) for geomorphic mapping in areas where recent urbanization has concealed the geomorphic markers.

Blind Thrusting, Surface Folding, and the Development of Geological Structure in the Mw 6.3 2015 Pishan (China) Earthquake

“…Our study, along with the results of Copley (2014), Copley and Reynolds (2014), and Mackenzie et al (2016), shows that it is not always valid to assume that fold growth above blind reverse faults is coseismic or that it is appropriate to model it as an elastic dislocation. Even in cases where folds and coseismic uplift have been seen to match topography, such as at the Coalinga anticline, Stein and Ekström (1992) reported that a modest fraction of the folding was postseismic, so at best modeling all fold growth as coseismic is likely to overestimate the coseismic moment release rate.…”

“…The observations presented above allow us to place some constraints on the mechanisms controlling topographic growth at the northern Tibetan range front and its timing within the seismic cycle. Recent work on reverse faults has attributed topographic growth to various mechanisms depending on setting, including: coseismic slip (Le Béon et al, 2014;Stein & Ekström, 1992), postseismic afterslip on a single fault (Copley, 2014;Elliott et al, 2015Elliott et al, , 2016Stein and Ekström, 1992;Zhou et al, 2016), afterslip on multiple faults (Copley & Reynolds, 2014;Mackenzie et al, 2016) and slip on faults or sections of fault that play an apparently minor part in the region's seismic activity (Mackenzie et al, 2016;Melnick, 2016;Whipple et al, 2016).…”

Active Tectonics Around Almaty and along the Zailisky Alatau Rangefront

“…We analyzed recent and past Google Earth imagery (1984–2017; DigitalGlobe–Landsat/Copernicus, Cnes/SPOT), the SPOT6 data, and declassified Corona satellite imagery (~2 m resolution) from the 1960s. The latter has the advantage of covering a time at which some tectonic features were not yet obliterated by urban development and infrastructure projects (Mackenzie et al, ).…”

Active faulting within a megacity: the geometry and slip rate of the Pardisan thrust in central Tehran, Iran

“…The North and South Rey scarps are dotted due to uncertainty about whether they are formed by faulting. Talebian et al 2004;Walker 2006;Walker et al 2010Walker et al , 2013Copley 2014;Copley & Jolivet 2016;Mackenzie et al 2016). To examine the geomorphology we combine an interpretation of the landscape from old aerial photographs with an analysis of a high-resolution digital elevation model (DEM) that we generate from sub-metre stereo satellite imagery.…”