25,000 Years Long Seismic Cycle in a Slow Deforming Continental Region of Mongolia

Abstract

The spatial distribution of large earthquakes in Slowly Deforming Continental Regions (SDCR) is poorly documented and, thus, has often been deemed to be random. Unlike in high strain regions, where seismic activity concentrates cyclically along major active faults, earthquakes in SDCR may seem to occur more erratically in space and time. This questions classical fault behavior models, posing paramount issues for seismic hazard assessment. Here, we investigate the M7, 1967, Mogod earthquake in Mongolia, a region recognized as a SDCR. Despite the absence of visible cumulative deformation at the ground surface, we found evidence for at least 3 surface rupturing earthquakes during the last 50,000 years, associated to a slip-rate of 0,06 ± 0,01 mm/yr. These results show that in SDCR, like in faster deforming regions, deformation localizes on specific structures. However, the excessive length of return time for large earthquakes along these structures makes it more difficult to recognize earthquake series, and could conversely lead to the misconception that in SDCR earthquakes would be randomly located. Thus, our result emphasizes the need for systematic appraisal of the potential seismogenic structures in SDCR in order to lower the uncertainties associated with the seismogenic sources in seismic hazard models.

Probing the Upper End of Intracontinental Earthquake Magnitude: A Prehistoric Example From the Dzhungarian and Lepsy Faults of Kazakhstan

“…High-magnitude intraplate events and the proposed two rupture scenarios (RS1 and RS2) are labeled in green and are highlighted by their names on the 1889 M w 8.0-8.3 Chilik, the 1905 M w 8.2-8.5 Bulnay, the 1911 M w 7.8-8.0 Chon-Kemin, the 1957 M w 8.1 Gobi-Altay earthquakes (Abdrakhmatov et al, 2016;Arrowsmith et al, 2017;Krüger et al, 2017;Kulikova & Krüger, 2015;Kurtz et al, 2018;Rizza et al, 2015). Other intraplate events (green) and renowned interplate (blue) are labeled by numbers for (1) the 1931 Fuyun (M w 7.9), (2) the 2013 Balochistan (M w 7.7), (3) the 1920 Haiyuan (M w 7.9), (4) the 1967 Mogod (M w 7.1), (5) the 2010 Darfield (M w 7.1), (6) the 1992 Landers (M w 7.3), ( 7) the 1999 Chi-Chi (M w 7.6), (8) the 2005 Sumatra (M w ∼ 9), (9) the 2011 Tohoku (M w ∼ 9), and (10) the 1855 Wairarapa earthquakes (Avouac et al, 2014;Bollinger et al, 2021;Catherine et al, 2005;Klinger et al, 2011;Ma & Mori, 2000;Ou et al, 2020;Quigley et al, 2012;Rodgers & Little, 2006;Satake et al, 2013;Sieh et al, 1993).…”