Instrumental magnitude constraints for the 11 July 1889, Chilik earthquake
Published:January 01, 2017
Frank Krüger, Galina Kulikova, Angela Landgraf, 2017. "Instrumental magnitude constraints for the 11 July 1889, Chilik earthquake", Seismicity, Fault Rupture and Earthquake Hazards in Slowly Deforming Regions, A. Landgraf, S. Kübler, E. Hintersberger, S. Stein
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A series of large-magnitude earthquakes above 6.9 occurred in the northern Tien-Shan between 1885 and 1911. The Chilik earthquake of 11 July 1889, has been listed with a magnitude of 8.3, based on sparse macroseismic intensities, constrained by reported damage. Despite the existence of several juvenile fault scarps in the epicentral region, that are possibly associated with the 1889 earthquake, no through-going surface rupture having the dimensions expected for a magnitude 8.3 earthquake has been located – a puzzling dilemma. Could the magnitude have been overestimated? This would have major implications not only for the understanding of the earthquake series, but also for regional hazard estimates. Fortunately, a fragmentary record from an early Rebeur–Paschwitz seismometer exists for the Chilik event, recorded in Wilhelmshaven (Germany). To constrain the magnitude, we compare the late coda waves of this record with those of recent events from Central Asia, recorded on modern instruments in Germany and filtered with Rebeur–Paschwitz instrument characteristics. Additional constraints come from disturbances of historic magnetograms that exist from the Chilik and the 1911 Chon-Kemin earthquakes. Scaling of these historic records confirm a magnitude of about 8 for the 1889 Chilik earthquake, pointing towards a lower crustal contribution to the fault area.
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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.