Focus on Myanmar
Home to more than 50 million people, Myanmar is shaped like a giant kite with a long tail that sweeps down along the Andaman Sea.
Beneath the surface, invisible dangers affect Myanmar’s growing population, making it one of the most earthquake-prone countries in the world. In the north, mountain ranges mark the northeast limit of the Indian tectonic plate, which has been colliding with the southern edge of the Eurasian plate for tens of millions of years. It is this interaction that has helped push up the Himalayan Mountains and the Tibetan Plateau in the far north of the country.
To the east, the Shan Plateau rises high above the central Myanmar basin. Ribbed with mountain ranges and broken hills, it hides a 700-kilometre-wide system of active faults, creating hazards we know little about.
Extending north to south, the 1,500-kilometre-long Sagaing Fault splits Myanmar in half, running below the economic centre of Mandalay, through the new capital of Nay Pyi Taw, alongside the thriving metropolis of Bago, and to the west of the country’s largest city, Yangon. When set into motion, strike-slip faults like this one tear the earth apart when slabs of crust slide sideways against each other.
Digging up data
Scientists at the Earth Observatory of Singapore have been locating, analysing, and assessing seismic faults of Myanmar and adjacent regions to better understand their potential hazards. Professor Kerry Sieh and his team are collecting data from satellites high above the earth, surveying the ground with instrument-carrying drones, monitoring ground-motion information gathered by seismic stations, and even digging deep below the ground in search of clues left by past events, a technique known as paleoseismology.
In one project led by Research Fellow Dr Xuhua Shi, he and his collaborators have been using fault geomorphology and paleoseismology to study sections of the Jinghong Fault, one of the primary faults on the Shan Plateau that crosses the China-Myanmar border. They tracked the fault-related ridges, valleys, and surface offsets there, dug trenches, and studied the sediments which were deformed by past earthquake ruptures. From this information, they mapped the northeast reach of the fault in detail, locating where geomorphic surfaces and sediments had changed as a result of past seismic ruptures, surveyed the topography by unmanned-aerial-vehicle-based photogrammetry, and determined the rate of the fault movement and the return time of strong earthquake events. From their research, Prof Sieh’s team estimated that the last major quake took place there between 500 and 1,000 years ago and estimated a recurrence rate of about 1,000 years.
Information from paleoseismological excavations, along with data from a variety of other sources, provided the foundation for a second project led by Research Fellow Dr Chan Chung-Han. He was tasked with developing high-quality probabilistic seismic-hazard maps for all of Southeast Asia, using uniform assessments and reliable data to replace current resources, which rarely matched well across national borders.
Dr Chan tested different approaches for seismic hazard evaluation by comparing analytical expectations to damage caused by actual events. They analysed that information to identify best-fitting models, and then used those models to develop a new set of hazard maps.
In Myanmar, the team’s surveys showed high hazard levels along the Sagaing Fault, which runs under many of the most populated areas of the country but has a short earthquake recurrence interval. Equally pressing, Dr Chan found, were threats to the more numerous low- and moderate-hazard areas of the region. In these areas, smaller events happening more often were likely to have devastating effects on vulnerable populations: Even a small earthquake in an unprepared area can have catastrophic consequences. The team also developed new ways of assessing whether earthquakes might trigger tsunamis, a constant worry for a country made up of hundreds of islands and with thousands of kilometres of coastline.
One way the team is addressing these concerns is by partnering with temblor.net, an online platform that integrates information on natural hazards from around the world and makes them available to scientists and the general public.
For the past decade, Professor Paul Tapponnier’s team has been working with colleagues from Myanmar to map active faults across the country, and to find the trace of large earthquakes in the past. When two recent deep earthquakes shook the area in central Myanmar, Prof Tapponnier’s team used video footage from social media users in Myanmar to analyse the pattern of ground motions and damages. They found that the pattern of ground motions from these two events changed significantly from one to the other, revealing complexities in forecasting the seismic hazard for Southeast Asia.
Last year, the team also looked closely at an active fault that extends beneath the Yangon metropolitan area. Using a new model to reinterpret the old data, they determined that the earthquake that occurred in 2017 was sourced from the same fault system that shook the region in 1927 and 1970. The epicentre of the 1970 earthquake was only a few kilometres from the western bank of the Yangon River, on the Irrawaddy Delta. The thick, soft sediments there, and the active fault hidden beneath the Delta, adds additional risk for local communities, since the spongy soil is likely to amplify any ground motion from earthquakes near the city.
Working farther north, Assistant Professor Shengji Wei and his team spent much of the year installing 29 broadband seismometers in the central Myanmar region. These instruments measure ground motion and detect the presence of seismic waves.
Along with eight seismometers put in place by the U.S. Geological Survey, the installations together create a network of 37 stations, each providing continuous data, and all feeding information to the new Myanmar National Seismic Network. When the real-time software detects the presence of an earthquake above magnitude 1.5, it automatically determines the event’s coordinates, magnitude, and origin time. Using the waveform records of local and distant earthquakes, researchers can determine the structure below the seismic station, geometry and locking status of the fault, existence of secondary faults, and even the possibility of an earthquake triggering a tsunami.
Between August and September of 2017, more than 300 local events were detected, expanding knowledge of the area and adding valuable information for both local and global study.
New data and models
Associate Professor Emma Hill’s team has begun looking in detail at data recorded by 24 continuous-GPS (cGPS) stations in the Myanmar-India-Bangladesh-Bhutan (MIBB) network. Each cGPS station works by continuously gathering location information from satellites and feeding the data to a complex database. The team also had access to nine new cGPS sites installed in central Myanmar in 2017. Computer models based on this data allow researchers to measure the speed and nature of the collision between India and Eurasia down to the millimetre, detecting both long-term changes and any sudden shifts.
In partnership with the Myanmar Survey Department, Hill’s team — led by Research Fellows Drs Eric Lindsey and Wang Yu, along with Research Associate Dr Lin Thu Aung — also revisited more than 80 survey benchmarks across Myanmar that were installed up to 15 years ago, re-measuring each of them with precise GPS to determine how much the ground in each area had moved. They created maps and models designed to pinpoint areas of underground instability and strain. One model created by PhD student Mr Rishav Mallick shows that a major fault under Bangladesh, which is locked in place and under constant, long-term strain, is creating potential hazards for the whole region, including Myanmar.
The work of Hill’s team in modelling the tectonic makeup of Myanmar also takes into account the seasonal monsoon rains, which cause flooding, land loss, and seasonal ground subsidence due to the massive weight of the water. These pressures interfere with efforts to gather data by overwhelming signals from small tectonic events. Working with visiting students from several countries, however, the team are correcting the signals using space-based gravity observations so they can see long-term tectonic trends without interference from monsoon rains.
In another study, the team processed data from Japanese satellites to find an increase in long-term subsidence (sinking land) in the area surrounding Yangon. While the city itself remains fairly stable, communities located beyond the reach of the municipal water-distribution system are using significant amounts of groundwater, exacerbating the problem of soils caving in and lands sinking. In some places, the land is subsiding at a rate of up to five centimetres a year.
In Myanmar, our researchers have learnt much from local and regional experts, but they’ve also shared knowledge and techniques with colleagues and communities.
In March of this year, Observatory scientists held another paleoseismology training workshop on the plate-boundary Sagaing Fault, focusing on the giant earthquakes generated by the Fault in the past 2,000 years. During this workshop, an international team of experts taught students from Myanmar, Thailand, Taiwan, and the USA the essential field skills of studying active faults and prehistoric earthquakes, including generating high-resolution digital maps using aerial photos taken by drones.
The goal of the course was to equip students with new skills and knowledge and to empower them to conduct fundamental geological research in their own countries. In this way, as in so many others, the Earth Observatory of Singapore continues to work toward building the resources needed to safeguard the health, safety, and economic potential of Southeast Asia.
- Late Quaternary paleoenvironments of the Kallang River Basin, Singapore
- EOS participation in “Hazards, Tipping Points, Adaptation and Collapse in the Indo‐Pacific World,” a project integrating history and science
- Investigating the geomicrobiology of storm and tsunami deposits
- Spatial and temporal variations in stable isotopic compositions of precipitation in Southeast Asia
- Reconstructing rates and magnitudes of Holocene sea-level change from Southeast Asia
- Continuous haze monitoring in Sumatra
- Sediment transport processes under tsunami waves—A case study of tsunami deposits in a coastal cave in Aceh, Sumatra
- Characterising coral open-system behaviour by high-precision U/Th dating: A case study in Sumba Island, Indonesia
- Lithosphere dynamics: From regional to global scale
- The strength of the lithosphere from geodetic to geologic time-scales
- Sumatran tectonic geodesy
- Slip rates and base level changes on the Main Frontal Thrust, Nepal
- Structural geology and hazards of the Sumatran accretionary wedge
- A quantitative reappraisal of Historical Earthquakes in Indonesia from uniformly assessed macroseismic observations from the Dutch colonial period
- Search for the impact crater of the Australasian tektites
- Paleoseismology and paleogeodesy of the Sumatran Subduction Zone
- Constraining short- and long-term tectonic deformation above the Manila Trench, Western Luzon, Philippines
- Interaction of geohazards and settlements through the past millennium, Banda Aceh, Indonesia
- Singapore-WiscAr Partnership (SWAP)
Satish Singh and Paul Tapponnier
- MIRAGE (Marine Investigation of the Rupture Anatomy of the 2012 Great Earthquake)
- MEGA-TERA (Mentawai Gap Tsunami Earthquake Risk Assessment)
Paul Tapponnier and Paramesh Banerjee
- Searching for the trace of great medieval earthquakes in central Nepal
- The Bengal‐Assam syntaxis: Geometry and kinematics of active faulting
- Earthquake ruptures in China: Testing earthquake recurrence models
- Discrete element modelling of faulting in collision zones (spherical lithosphere geometry)
- Revisit tsunami earthquakes in Sunda Subduction Zone with new dataset and waveform modelling approaches
- SE Asia seismology
Caroline Bouvet de la Maisonneuve
- Investigating cycles of caldera formation at Rabaul, Papua New Guinea
- Time scales of volcanic unrest and dynamics of magma ascent
- Pattern recognition of crystal zoning as a means to quantify volcanic processes
- Lab volcanoes
- Volcanic Eruption: Location and characterisation using infrasound
- Models constraining models: Analogue modelling to assess theoretical uncertainties
HAZARDS AND SOCIETY
- Aid governance, resilience, and community-driven reconstruction in urban settlements in the Kathmandu Valley following the 2015 earthquake
- The aftermath of aid
- EOS Classroom Companions
- The Tsunami of New Dreams
- Earth Girl Volcano
- EOS Art Projects
- Knowledge Capsules