Instrumental magnitude constraints for the 11 July 1889, Chilik earthquake

Abstract

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.

Active Tectonics Around Almaty and along the Zailisky Alatau Rangefront

“…The earthquake triggered numerous landslides (Mushketov, ) and led to several hundred fatalities (Hay, ). Only 2 years later, in 1889, the Chilik earthquake, with a magnitude of ~8, ruptured the surface 100 km to the southeast of Almaty and led to severe shaking in the city (Abdrakhmatov et al, ; Krüger et al, ). This earthquake produced ~175 km of surface ruptures and up to 10 m of surface slip (Abdrakhmatov et al, ; Figure b).…”

“…Beachballs show depth‐colored earthquakes with focal mechanisms from body waveform modeling of Sloan et al (). The location of the 1978 Dzhalanash–Tyup earthquake is marked (location from Krüger et al, , and focal data from CMT, ). White dots are earthquakes m b > 4.5 from the catalog of Engdahl et al () and updates thereof from 1960 to 2008 and the ISC catalog (ISC, ) from 2009 to 2016.…”

Shortening Accommodated by Thrust and Strike‐Slip Faults in the Ili Basin, Northern Tien Shan

“…In 1911, the M w 7.8–7.9 Chon‐Kemin earthquake (also referred to as the Kebin earthquake) resulted in almost 200 km of surface ruptures between Almaty and Lake Issyk Kul (Arrowsmith et al, ; Bogdanovich et al, ). Other significant earthquakes with magnitudes of M > 7 such as the 1887 Verny earthquake (Tatevossian, ) or the 1978 Dzhalanash‐Tyup event (Krüger et al, ) did not produce known surface ruptures.…”

“…Nearly half of the convergent motion between India and Eurasia is accommodated within the Tien Shan, more than 1,000 km north of the edge of stable India (Abdrakhmatov et al, ). This growing mountain range has seen some of the largest intracontinental earthquakes documented in the past 150 years (e.g., Krüger et al, ; Kulikova & Krüger, ; Molnar & Deng, ) and major faults with lengths of up to several hundred kilometers stand out in the geomorphology features (Avouac et al, ; Avouac & Tapponnier, ; Campbell et al, ). The Tien Shan hosts a large number of E‐W and NE‐SW elongated ranges, which are separated by intramontane and intermontane basins (Figure ).…”

Active tectonics, earthquakes and palaeoseismicity in slowly deforming continents

“…Mining-induced subsidence may also disguise surface effects of tectonic deformation. In the coal and lignite mining areas of Central and Western Germany and Western Poland, mining induced subsidence rates are on the order of cm a 21 -up to three orders of magnitude higher than tectonic slip rates (Perski 1998;Görres et al 2006;Görres 2008;Kratzsch 2012). Consequently, the worst environments for preservation of fault scarps are densely populated low-strain fault systems in humid or moderately humid climate zones, as exemplified by the tectonically active areas in Central Europe, South America and parts of China.…”