Surface rupture of the 1911 Kebin (Chon–Kemin) earthquake, Northern Tien Shan, Kyrgyzstan
Published:January 01, 2017
J. Ramón Arrowsmith, Christopher J. Crosby, Andrey M. Korzhenkov, Ernest Mamyrov, Irina Povolotskaya, Benny Guralnik, Angela Landgraf, 2017. "Surface rupture of the 1911 Kebin (Chon–Kemin) earthquake, Northern Tien Shan, Kyrgyzstan", Seismicity, Fault Rupture and Earthquake Hazards in Slowly Deforming Regions, A. Landgraf, S. Kübler, E. Hintersberger, S. Stein
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The 1911 Chon–Kemin (Kebin) earthquake culminated c. 30 years of remarkable earthquakes in the northern Tien Shan (Kyrgyzstan and Kazakhstan). Building on prior mapping of the event, we traced its rupture in the field and measured more than 50 offset landforms. Cumulative fault rupture length is >155–195 km along 13 fault patches comprising six sections. The patches are separated by changes of dip magnitude or dip direction, or by 4–10 km-wide stepovers. One <40 km section overlaps and is parallel to the main north-dipping rupture but is 7 km north and dips opposite (south). Both ends of the rupture are along mountain front thrust faults demonstrating late Quaternary activity. We computed the moment from each fault patch using the surface fault traces, dip inferred from the traces, 20 km seismogenic thickness, rigidity of 3.3×1010 N m−2 and dip slip converted from our observations of the largely reverse sense of motion vertical offsets. The discontinuous patches with c. 3–4 m average slip and peak slip of <14 m yield a seismic moment of 4.6×1020 Nm (Mw 7.78) to 7.4×1020 Nm (Mw 7.91). The majority of moment was released along the inner eastern rupture segments. This geological moment is lower by a factor of 1.5 from that determined from teleseismic data.
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Seismicity, Fault Rupture and Earthquake Hazards in Slowly Deforming Regions
Palaeoseismic records and seismological data from continental interiors increasingly show that these areas of slow strain accumulation are more subject to seismic and associated natural hazards than previously thought. Moreover, some of our instincts developed for assessing hazards at plate boundaries might not apply here. Hence assessing hazards and drawing implications for the future is challenging, and how well it can be done heavily depends on the ability to assess the spatiotemporal distribution of past large earthquakes. This book explores some key issues in understanding hazards in slowly deforming areas. Examples include classic intraplate regions, such as Central and Northern Europe, Mongolia, Inner Mongolia, Australia, and North and South America, and regions of widely distributed strain, such as the Tien Shan Mountains in Central Asia. The papers in this volume are grouped into two sections. The first section deals with instrumental and historical earthquake data and associated hazard assessments. The second section covers methods from structural geology, palaeoseismology and tectonic geomorphology, and incorporates field evidence.