Seismotectonics of the 2014 Chiang Rai, Thailand, earthquake sequence

Abstract

On 5 May 2014, a Mw 6.2 strike‐slip earthquake occurred in the Mae Lao region of Chiang Rai province in Thailand. This earthquake took place in a region of known faults and caused substantial damage and injuries, although the region had been previously identified as having a relatively low earthquake hazard. Detailed field reconnaissance and deployment of a dense, temporary, network of broadband seismometers allowed details of the damage and its relationship to seismicity to be analyzed. The aftershock sequence associated with this main shock occurs on two well‐defined trends, reflecting the two potential fault planes in earthquake mechanisms for the main shock and the majority of the aftershocks. The damage area was relatively large for an event of this magnitude, but building damage was largely limited to the primary rupture region, while liquefaction and other ground failure are spatially associated with the rupture area and along regional rivers. Stress modeling, combined with the time series and pattern of aftershock activity, leads us to propose that slip near the northern termination of the main shock rupture continued slightly onto a conjugate fault, helping to trigger the distinct pattern of two discrete, conjugate trends of aftershock activity that mirror the kinematics of the main shock fault mechanism.

Fault Slip and GPS Velocities Across the Shan Plateau Define a Curved Southwestward Crustal Motion Around the Eastern Himalayan Syntaxis

“…Numerous damaging earthquakes have occurred during the historic and instrumental periods on both the sinistral‐ and dextral‐slip faults throughout the Shan Plateau region (Figure ), suggesting that many (if not all) of these faults are active today. Examples of recent significant earthquakes on the sinistral‐slip faults, from northwest to southeast, include the 2011 M w 5.5 (Ekström et al, ) Yingjiang earthquake on the Dayingjiang fault (Fang et al, ; Lei et al, ), the 1976 M w 6.7 and 6.6 earthquake sequence on the Longling‐Ruili or nearby sinistral‐slip faults (Dziewonski et al, ; Gu, Lin, Shi, & Wu, ; Guo et al, ; Zuo et al, ), the 1950 M ~ 7 Daluo earthquake close to the central Jinghong fault near China/Myanmar border (Gu, Lin, Shi, & Li, ), the 2011 M w 6.8 Tarlay earthquake at the western end of the Nam Ma fault (Tun et al, ), the 2014 M w 6.1 Mae Lao earthquake on the Mae Lao fault (~30 km south of the Mae Chan fault) in northern Thailand (Pananont et al, ), and two moderate historic earthquakes along the Muang Houn fault zone in northern Laos (Pailoplee et al, ) (Figure and Table ). Moderate earthquakes that have occurred on the dextral‐slip faults on the Shan Plateau include the 2014 M w 5.7 and 5.9 earthquakes north of the Dayingjiang fault (Figure ) (Ekström et al, ; Yang et al, ), the 1988 M w 7.0 Lancang‐Gengma earthquake (Chen & Wu, ), the 1995 M w 6.8 Menglian earthquake along a nearly NW‐trending dextral‐slip fault to the south of the Menglian fault (Ji et al, ), and the 2014 M w 6.0 Jinggu earthquake along a dextral‐slip fault to the east of the Lancang fault (Ekström et al, ; Xu et al, ).…”

Structural interpretation of Mae Suai Basin, Chiang Rai Province, based on gravity data analysis and modelling

“…Relocation of earthquake epicenters of the 2014 Earthquakes by Noisagool et al. (2016) and Pananont et al. (2017) (Fig.…”

“…On 5 May 2014 at 11:08:43 UTC, a M6.1 earthquake, the Mae Lao earthquake, the largest earthquake magnitude recorded in Thailand this decade, occurred at ∼6 km depth in northern Thailand (U.S. Geological Survey: USGS, 2014) with an epicenter located at latitude 19.69 o N and longitude 99.69 o E in Pan District. Pananont et al. (2017) suggested the main shock was generated on NNW-SSE trending Phayao Fault Zone, with dominantly right lateral strike-slip motion (Fig.…”

“…Focal mechanism solutions indicate an ENE-WSW trending fault with a strike-slip movement sense caused the aftershock series (Fig. 2b) (Noisagool et al., 2016; Pananont et al., 2017). Earthquake locations and vibrations were thought to be related regarding orientation and behaviour to the movement on the Mae Lao Fault Segment of the Phayao Fault Zone (Figs.…”

“…Therefore, this recently significant earthquake event leads the Mae Suai Basin (MSB) to be an area of interest for surface and subsurface investigations.

Fig. 2a) Seismicity of Northern Thailand and surrounding regions showing earthquakes generated before the 2014 Earthquake main shock (grey circles), and the 2014 main shock and seismicity after that time up to late 2015 (red circles) (modified from Pananont et al., 2017). b) The Regional moment tensor solutions showed focal mechanisms for 27 Earthquakes (Fig.

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