Active faults and the devastating earthquakes they can trigger do not respect political borders. Whilst the recent earthquakes in Nepal did most damage to the mountain kingdom itself, hundreds of people were also killed or injured in neighbouring China, India and Bangladesh.
The region’s history tells a similar story – the three countries’ earthquake records over the last 500 years are intertwined by shared proximity to the Himalayan mountain belt and its underlying megathrust fault.
Ways of improving resilience to earthquake hazard also need to transcend political boundaries, bringing together scientists and policymakers from the affected countries to share knowledge, experience and ideas.
This principle has led to the Earthquakes without Frontiers (EwF) partnership – a diverse group of natural and social scientists from around the UK. Led by James Jackson of both COMET and the University of Cambridge, EwF is a 5-year initiative funded by NERC and ESRC (the Natural Environment and Economic and Social Research Councils) under the Improving Resilience to Natural Hazards programme.
As well as COMET, the partnership includes researchers from Cambridge, Durham, Hull, Leeds, Northumbria and Oxford Universities, the British Geological Survey, the Overseas Development Institute and Durham’s Institute of Hazard, Risk and Resilience.
The project focuses on three broad regions – China, the Himalayan mountain front (Nepal and Northern India) and Central Asia (Kazakhstan and Kyrgyzstan) – with the key objective of furthering knowledge on earthquakes and landslides in the continental interiors.
Much of this involves using remotely sensed data which complements the project’s cross-border approach. EwF scientists use digital topography and multispectral and optical imagery to research landslide hazard and map active faults, alongside satellite radar to measure the warping of the Earth’s crust and steady interseismic motions as faults build up stress before the next seismic event.
All of this contributes to a wider programme of social and natural scientific research with scientists in the partner countries, as well as being used to run workshops and training events for young international scientists.
Crucially, this knowledge exchange extends to countries dealing with similar hazards – the same types of fault that threaten vast regions in China also cause earthquakes in Italy, and lessons learnt about Iranian faults can inform work on hazard in Kazakhstan and vice versa. As such, EwF brings together scientists from many countries to share knowledge and experience across an even wider network, culminating in the annual EwF partnership meetings, the most recent of which was held in Kathmandu in April 2015.
When a huge Mw7.8 earthquake struck Nepal on the 25th April, it came as a double blow to all within EwF. Nepal is not only one of our focus areas, but many of the UK team also had been in Kathmandu just one week before the earthquake, working and living alongside Nepali colleagues and friends.
The International Charter for Space and Major Disasters was invoked just 3 hours after the earthquake, and over the following few days, space agencies hurriedly tasked their satellites to acquire new imagery over Nepal. We all felt strongly that we should put our combined experience to good use in the immediate aftermath of the Nepal earthquake, and dashed to obtain satellite imagery of the area. In the weeks since we have been working to analyse this imagery in order to aid both disaster relief efforts and hazard re-evaluation.
EwF researchers, along with colleagues at the University of Leeds, used data from the European Space Agency’s Sentinel-1A satellite to measure how the ground was permanently warped by the earthquake. This was greatly assisted by COMET’s new automated processing facility, designed to cope with the vast amount of data from the Sentinel-1 satellites, which helped to produce some of the first radar interferograms of the Nepal earthquake. These mapped how the ground was warped along a 170 km stretch of the fault, moving by up to ~1.4 m near Kathmandu.
We are now modelling the data to understand how the fault slipped at depth, establish the relationship with the large Mw 7.3 aftershock on the 12th May, and gauge how these events may have stressed the surrounding regions, making them more likely to fail in future.
At the same time, EwF scientists at Durham University and the British Geological Survey have been using high-resolution optical and multispectral imagery to map landslides in the region. We have identified around 3,600 landslides that were either triggered or reactivated by the earthquake, using the maps to show where rivers are likely to be dammed and roads blocked. This has also highlighted the need to plan for the monsoon season which may reactivate or trigger even more deadly landslides.
Over the coming months, EwF researchers will continue to work on these topics as well as the many more questions raised by the Nepal earthquake. We hope that the lessons learned from this terrible event will bring us one step closer to improving resilience to future earthquakes, not just for Nepal and the countries across its borders, but for all earthquake-prone countries.
This is an abridged version of an article that appears in the current newsletter of the Geological Remote Sensing Group.