Earthquakes and slip rate of the southern Sagaing fault: insights from an offset ancient fort wall, lower Burma (Myanmar)

Field investigations of an ancient fortress wall in southern Myanmar reveal an offset of ~6 m across the Sagaing fault, the major right-lateral fault between the Sunda and Burma plates. The fault slip rate implied by offset of this 16th-century fortress is between 11 and 18 cm yr^(–1). A palaeoseismological excavation within the fortress reveals at least two major fault ruptures since its construction. The slip rate we obtained is comparable to geodetic and geological estimates farther north, but is only 50 per cent of the spreading rate (38 mm yr^(–1)) at the Andaman Sea spreading centre. This disparity suggests that other structures may be accommodating deformation within the Burma Plate. We propose two fault-slip scenarios to explain the earthquake-rupture history of the southern Sagaing fault. Using both small offset features along the fault trace and historical records, we speculate that the southern Sagaing fault exhibits a uniform-fault-slip behaviour and that one section of the fault could generate a M7+ earthquake within the next few decade

Shallow Rupture of the 2011 Tarlay Earthquake (M_w 6.8), Eastern Myanmar

We use L‐band Advanced Land Observation Satellite PALSAR data to infer the distribution of subsurface fault slip during the Tarlay earthquake (M_w 6.8) in eastern Myanmar. We find the total length of surface rupture is approximately 30 km, with nearly 2 m maximum surface offset along the westernmost section of the Nam Ma fault (the Tarlay segment). Finite‐fault inversions constrained by Interferometric Synthetic Aperture Radar (InSAR) and pixel‐tracking data suggest that fault slip is concentrated within the upper 10 km of the crust. Maximum slip exceeds 4 m at a depth between 3 and 5 km. Comparison between field measurements and near‐fault deformation obtained from the InSAR range‐offset result suggests about 10%–80% of displacement occurred within a 1 km wide zone off the main surface fault trace. This off‐fault deformation may explain the shallow slip deficit that we observed during this earthquake. We estimate a recurrence interval for Tarlay‐like events to be 1600–6500 yrs at this section of the Nam Ma fault. A detailed paleoseismological study is essential to clarify the slip behavior and the earthquake recurrence interval of the Nam Ma fault

Active tectonics and earthquake potential of the Myanmar region

This paper describes geomorphologic evidence for the principal neotectonic features of Myanmar and its immediate surroundings. We combine this evidence with published structural, geodetic, and seismic data to present an overview of the active tectonic architecture of the region and its seismic potential. Three tectonic systems accommodate oblique collision of the Indian plate with Southeast Asia and extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Subduction and collision associated with the Sunda megathrust beneath and within the Indoburman range and Naga Hills accommodate most of the shortening across the transpressional plate boundary. The Sagaing fault system is the predominant locus of dextral motion associated with the northward translation of India. Left-lateral faults of the northern Shan Plateau, northern Laos, Thailand, and southern China facilitate extrusion of rocks around the eastern syntaxis of the Himalaya. All of these systems have produced major earthquakes within recorded history and continue to present major seismic hazards in the region

Evidence of Quaternary and recent activity along the Kyaukkyan Fault, Myanmar

Cenozoic right-lateral shear between the eastern Indian margin and Eurasia is expressed by numerous N-S trending fault systems inboard of the Sunda trench, including the Sagaing Fault. The most easterly of these fault systems is the prominent ∼500 km long Kyaukkyan Fault, on the Shan Plateau. Myanmar’s largest recorded earthquake, Mw 7.7 on 23rd May 1912, focused near Maymyo, has been attributed to the Kyaukkyan Fault, but the area has experienced little significant seismicity since then. Despite its demonstrated seismic potential and remarkable topographic expression, questions remain about the Kyaukkyan Fault’s neotectonic history. In this study we document robust geologic evidence of fault activity along the Kyaukkyan Fault. Field investigation and interpretation of satellite imagery reveal deformation features developed along a fault system mostly indicative of Quaternary dextral strike-slip faulting. Clearly defined tectonic geomorphology, including fault scarps and linear valleys, are used to trace the northernmost and southernmost part of the fault. The fault’s central section is characterised by a complex pull-apart system, whose normal border faults show signals of relatively slow recent activity. Dextral transtensional activity along the Kyaukkyan Fault is recorded by geomorphic features such as sag ponds, shutter ridges, offset and beheaded streams, triangular facets and low-sinuosity mountain fronts. The Quaternary age of activity is demonstrated by short-lived geomorphic features such as wind-gaps, offset and deformed alluvial fans, and even offset of man-made structures. In the Inle basin, alluvial fan successions along the easternmost mountain front reveal a vertical transition from faulted and folded alluvial fan sequences adjacent to pre-Cenozoic flanking ranges, to overlying gravels that appear less deformed. Conversely, a locally buried cross-basin fault system has fresh geomorphic expression even within the uppermost parts of the lacustrine/fluvial basin fill. This may indicate Quaternary migration of dominant fault deformation from sidewall faults to a cross-basin fault system, which is indicative of a mature strike-slip fault system and has been observed in other active strike-slip faults around the world and in analogue models.Published207-2252TR. Ricostruzione e modellazione della struttura crostaleJCR Journa

Confirmation of Skywalker Hoolock Gibbon (Hoolock tianxing) in Myanmar extends known geographic range of an endangered primate

Characterizing genetically distinct populations of primates is important for protecting biodiversity and effectively allocating conservation resources. Skywalker gibbons (Hoolock tianxing) were first described in 2017, with the only confirmed population consisting of 150 individuals in Mt. Gaoligong, Yunnan Province, China. Based on river geography, the distribution of the skywalker gibbon has been hypothesized to extend into Myanmar between the N’Mai Kha and Ayeyarwaddy Rivers to the west, and the Salween River (named the Thanlwin River in Myanmar and Nujiang River in China) to the east. We conducted acoustic point-count sampling surveys, collected noninvasive samples for molecular mitochondrial cytochrome b gene identification, and took photographs for morphological identification at six sites in Kachin State and three sites in Shan State to determine the presence of skywalker gibbons in predicted suitable forest areas in Myanmar. We also conducted 50 semistructured interviews with members of communities surrounding gibbon range forests to understand potential threats. In Kachin State, we audio-recorded 23 gibbon groups with group densities ranging between 0.57 and 3.6 group/km2. In Shan State, we audio-recorded 21 gibbon groups with group densities ranging between 0.134 and 1.0 group/km2. Based on genetic data obtained from skin and saliva samples, the gibbons were identified as skywalker gibbons (99.54–100% identity). Although these findings increase the species’ known population size and confirmed distribution, skywalker gibbons in Myanmar are threatened by local habitat loss, degradation, and fragmentation. Most of the skywalker gibbon population in Myanmar exists outside protected areas. Therefore, the IUCN Red List status of the skywalker gibbon should remain as Endangered

The latest middle Eocene Primate Fauna in Pondaung area, Myanmar

So far four primate taxa have been discovered from the latest middle Eocene Pondaung Formation, Central Myanmar (=Burma): Pondaungia cotteri, Amphipithecus mogaungensis, Bahinia pondaungensis, and an unnamed new taxon. Especially the phylogenetic positions of Pondaungia and Amphipithecus have been discussed by many researchers since their first discoveries in the early part of this century. Recent new specimens, including maxillary fragments, of Pondaungia and Amphipithecus may reveal then taxonomic status and phylogenetic position in the evolution of early anthropoids in East Asia

A preliminary report on the Eocene mammals of the Pondaung fauna, Myanmar

A diverse array of mammalian species is now known from the Pondaung Formation, located in central Myanmar. The new mammals for the Pondaung fauna are: Anthropoidea gen. et sp. nov. (Primates); Hyaenodontidae indet. A, and indet. B (Creodonta); ?Phiomyidae indet. C (Rodentia); Ungulata indet. D; ?Agriochoeridae indet. E (Artiodactyla); cf. Ilianodon (Rhinocerotoidea; Perissodactyla); Amynodontidae indet. F (Perissodactyla). The stratigraphical and microfossil evidences suggest that the Pondaung Formation is referable to the period from the middle to late Eocene. Concerning the dating of the Pondaung mammal fauna, middle middle to late Eocene (most probably late middle Eocene) is suggested based on comparisons of it with other Eocene mammal fauna; however, further information is necessary to identify the date more precisely