Two seismic gaps on the Sagaing Fault, Myanmar, derived from relocation of historical earthquakes since 1918

Abstract

Relocation of six M (magnitude) ≥ 7.0 earthquakes near the Sagaing Fault in Myanmar since 1918 allows us to image earthquake history along the Sagaing Fault. All the earthquakes were relocated on the Sagaing Fault by using the modified joint hypocenter determination method. Combining the relocated epicenters with information on foreshocks, aftershocks, seismic intensities, and coseismic displacement, we estimated the location of the fault plane that ruptured during each earthquake. This analysis revealed two seismic gaps: one between 19.2°N and 21.5°N in central Myanmar, and another south of 16.6°N in the Andaman Sea. Considering the length of the first seismic gap (∼260 km), a future earthquake of up to M ∼7.9 is expected to occur in central Myanmar. Because Nay Pyi Taw, the recently established capital of Myanmar, is located on the expected fault, its large population is exposed to a significant earthquake hazard.

Chapter 2 Active tectonics of Myanmar and the Andaman Sea

“…2.2). Next, two earthquakes struck north of Mandalay in September 1946 on adjacent fault segments, three minutes apart (M b 7.5 and M s 7.8; Hurukawa & Maung Maung 2011). In this same area, three M w > 6 earthquakes occurred in 1991, 1992.…”

“…Major earthquakes (M s ≥7) are shown by yellow stars for the period 1900-76 from International Seismological Centre (2011) and by red stars for the period 1836-1900 from Le Dain et al (1984). The location and magnitude of the M b 7.5 1946 earthquake is taken from Hurukawa & Maung Maung (2011). Earthquake focal mechanisms are taken from the GCMT catalogue (Ekstrom et al 2005) and show M w ≥5.5 earthquakes, listed as being shallower than 30 km in the period 1976-2014.…”

Coulomb stress transfer and accumulation on the Sagaing Fault, Myanmar, over the past 110 years and its implications for seismic hazard

“…Therefore, in this study, we focused on the earthquakes with M > 6.5. Hence, we compiled an earthquake sequence consisting of 10 events (Figure and Table ) by picking 8 from Hurukawa and Maung Maung [] and 2 from Maurin et al [] and Kundu and Gahalaut []. The locations of 9 out of 10 earthquakes are evidenced by ruptures on surface confirmed by field work [ Wang , ], except the 1931 earthquake, the locations of hypocenter and rupture of which is still enigmatic.…”

“…Map shows location of the SF region and 10 earthquakes ( M > 6.5) along the fault from 1906 to 2003. The open red circles and beach balls display the proposed [ Maurin et al , ; Kundu and Gahalaut , ; Hurukawa and Maung Maung , ] and the modified epicenters in this study, respectively. The black beach balls indicate the large historical earthquakes.…”

“…The 1906 and 1908 events are taken from Maurin et al [] and Kundu and Gahalaut [], and the others are from Hurukawa and Maung Maung []. μ ′, effective coefficient of friction; Δ σ c , coseismicΔCFS; Δ σ c + p , coseismic + postseismicΔCFS; Δσ max , Δ σ ave , maximum and averaged ΔCFS on the rupture.…”