Southeast Asia and its surrounding regions have many large, active faults, as well as a number of major subduction zones that are responsible for some of the world’s biggest earthquakes. The tectonics research group at EOS aims to understand and increase fundamental knowledge of the region’s tectonic and seismic behaviour, to identify signs of previous earthquakes and tsunamis, their size, their recurrence, and their capacity for destruction.
Active tectonics of the past
Professor Paul Tapponier reads landscapes. He can see signs of evolution of the landscape –evidence such as disrupted river beds, escarpments and terraces. He and his colleagues and students then date these events and reconstruct the three dimensional tectonic blocks and faults with their associated earthquakes and, thereby, identify the seismic hazard of large regions. Judith Hubbard ‘reads’ the buried landscape from the topography of buried sediments and structures.
Professors Kerry Sieh and Charlie Rubin also study the past earthquake history from geological layers and landforms to understand the geometries of active faults, the earthquakes they generate, and the crustal structure their movements produce.
Active tectonics in the present
EOS scientists also study the very fast, dynamic processes associated with rapid breakage of Earth’s rocks. Geodesists such as Emma Hill look at the current deformation of the Earth’s surface. Her research group uses these surface measurements to infer the mechanics of earthquakes and the slow processes that prepare the earth for strong shaking. When an earthquake occurs, geodesists can actually see the rapid movement at the earth’s surface. Understanding the modern behaviour is another piece of the puzzle that gives a complete look at the earthquake cycle.
Observational seismologist Shengji Wei uses seismic waveforms at wide distance ranges (from near field to thousands of kilometres away) and frequency ranges (several Hz to static) to determine fundamental source parameters of earthquake such as location, origin time, magnitude, focal mechanism and finite rupture process. These earthquake information are important proxies to understand the recent tectonic process and earthquake physics. Dr. Wei also conduct strong ground shaking simulations for large earthquakes, involving complicated rupture process and three-dimensional velocity structure, which are keys to understand the damages that an earthquake can generate.
To be able to forecast earthquakes like we forecast weather, we also need a full understanding of how rocks deform deep in the interior. Today there is tremendous uncertainty in how rocks behave under different pressure, temperature, and fluid conditions.
Scientists such as Sylvain Barbot produce simulations to incorporate many of these direct observation to explore a range of realistic scenarios.
Adam Switzer looks at the sediments and geomorphic forms from tsunami surge to help build the picture of long term earthquakes. Huang Zhenhua models the behaviour of earthquake’s associated tsunamis.
Earth scientists cannot predict earthquakes, but we can bring awareness to the possibilities of what might occur.