Coseismic deformation associated with the 11th November 2012 Shwebo earthquake, Myanmar

Earthquakes occur when blocks of the Earth's crust slide past east other along fractures called tectonic faults. Motion between crustal blocks is a result of tectonic processes such as formation of new oceanic crust at mid-ocean ridges, sinking of old crust into the interior of the Earth at subduction zones and collision between continental plates.

Friction and normal stresses across faults cause them to be inactive, or 'locked' most of the time. Motion between crustal fragments is accommodated by elastic bending of rocks either side of the locked fault. When the stress parallel to the fault becomes sufficient to overcome friction and normal stresses, the fault slips rapidly. Seismic waves are a result of this sudden release of elastic energy. They radiate through the crust and spread around the Earth in a matter of minutes. The magnitude of an earthquake is related to the length of the fault rupture, and the amount of elastic bending since the previous earthquake.

Today the Indian plate is moving north relative to Eurasia, accompanied by widespread seismicity. The Himalayan mountains are an expression of the convergence between these two continental plates since 50 million years ago. Along its eastern margin the Indian plate is sliding sideways past Indochina. More than half the annual motion across this sideways, or 'transform', plate boundary is focussed on the 1500 km-long Sagaing Fault in Myanmar.

Since 1918 there have been 6 major earthquakes (magnitude 7.0 to 7.9) along the Sagaing Fault. They were unequally distributed along the length of the fault, and a 260 km-long section remains un-ruptured. It is likely that this section is locked and may fail in a single large earthquake in the near future. The capital city of Myanmar, Nay Pyi Taw, straddles the Sagaing Fault in the centre of the un-ruptured section.

On 11/11/12, a magnitude 6.8 earthquake ruptured the Sagaing Fault at Shwebo, near Mandalay. The earthquake focus was at a shallow depth of about 10 km. Sixteen people were killed and fifty-two injured by the earthquake. Hundreds of houses, schools and religious buildings were damaged along a 150 km section of the Sagaing Fault. Aftershocks still continue.

The ultimate aim of this project is to mathematically model the state of stress along the Sagaing Fault. Stress modelling highlights where the fault is relaxed, and where stress is elevated. Earthquakes nucleate in areas of elevated stress. Data about previous earthquake ruptures is required to model the stress pattern along the fault. The 11th November Shwebo earthquake is the first large earthquake since Myanmar became accessible to foreign researchers, and offers an unprecedented opportunity to collect such data directly from the field.

During an earthquake like the Shwebo event, the sides of the fault will slide about 0.2-1 m past each other. This displacement will cause a surface rupture, with sideways and vertical displacements. Systematic mapping of the surface rupture quantifies the amount and direction of slip along the fault, and shows whether the fault at depth is a single fracture or more segmented. Mapping the terminations of the fault rupture gives important information about how rupture is arrested. For example, ruptures often terminate across large gaps in the main fault where there is subsidence.

This research will use surface rupture data collected within 3 months of the Shwebo earthquake to understand how rupture propagates along the Sagaing Fault, and to find where future earthquakes are likely, with particular attention to the fault immediately south of Mandalay, where a long section has conspicuously little historical seismicity. The research will be a collaboration between experts in structural geology, seismology and seismic hazard assessment in Europe and Myanmar. The results will be widely communicated so they may be used to inform development policy in Myanmar and other seismically active areas.

The main beneficiary is considered to be the planning and development departments of the Myanmar government. S.T.T. is on the Myanmar Earthquake Committee, tasked with assessing seismic hazards in Myanmar. They are able to disseminate the results of the research to policy makers and civil engineers. This information would be of benefit immediately, as central Myanmar is developing rapidly around Nay Pyi Taw. These beneficiaries would use the results of initial coseismic deformation investigation and later Coulomb stress modelling to determine which areas along the fault are at highest risk, and where structures, for example dams and bridges, need to be most carefully designed and placed.

The research will be of benefit to people living on or close to the Sagaing Fault, and the wider public in Myanmar, who are at a high risk from seismic hazards. The research will be communicated via an accessible website, and directly to schools in the region, with the aim of raising awareness of the fault. Simple precautions will be emphasised that will increase the chances of surviving an earthquake. If the results of the project indicate that the central locked segment of the Sagaing Fault is likely to produce a great earthquake, it will enable residents to take appropriate precautions, reducing the human and economic cost of an earthquake. If it is not, then economic development will not be needlessly hindered. This is one of the most important benefits of the research, and one that will produce an immediate improvement in the long-term health and quality of life of those living close to the fault.

Commercial beneficiaries include companies producing or exploring for hydrocarbons in Myanmar and SE Asia. These include BP, INPEX, Repsol and Nikko. A number of such companies are already members of the SE Asia Research Group, with which I.W. is closely affiliated, making dissemination of the work to them in the form of reports and presentations effective. The companies would benefit from the proposed research in the same way as they benefit from research done directly by the SEARG, as a means to understand basin-scale processes in a regional tectonic framework, and to incorporate field data that is impossible to acquire by a large oil company.

Other oil companies such Marathon and ENI are members of the Fault Dynamics Research Group, with which I.W. is also affiliated. They are interested in the 3-D architecture and structural evolution of faults. Field examples showing how major faults propagate and terminate are essential to their understanding of basin-scale systems imaged using only geophysical data. This work would benefit them in particular as the field example will be used to calibrate analogue models produced by the FDRG, on which oil companies base their understanding of fault evolution. Potential benefits of this impact will be risk-reduction in new exploration, and ultimately wealth generation for UK and foreign oil companies.

The research could be disseminated quickly and effectively to companies involved in the SEARG and FDRG. There is great interest in exploring for hydrocarbons in Myanmar since trade embargoes were dropped and bureaucracy simplified last year, so it is likely that the impact of the research would be on a timescale of <5 years.

Researchers in industrial mineral exploration, e.g. Wendy Richards at BP and Khin Zaw at the ARC Centre of Excellence in Ore Deposits, will learn how the Sagaing Fault is evolving, and how deformation along the central section at Mandalay relates to the offshore hydrocarbon-bearing section. The research will also provide information about 3-D geometry and development of strike-slip faults that will be of benefit to those studying fault-hosted mineral reserves. I.W. is in regular contact with both BP and ARC-CODES, and will be able to disseminate this information effectively. They will also be able to access the full results database via the project website.