Two of nature’s most destructive forces – earthquakes and tsunamis – may actually pose a greater threat than current estimates, according to new research from scientists at the University of New Mexico and the United States. ‘Nanyang Technological University published today in Geoscience of nature.
The researchers developed a new method to assess the earthquake and tsunami risks posed by the most remote part of the offshore subduction zones and found that the danger could have been systematically underestimated in some areas, this which means that the tsunami risk assessments would have to be redone based on the new findings. The findings have important implications for risk mitigation in affected areas around the world, including Southeast Asia and the Pacific region, in the event of future earthquakes and tsunamis.
The Megathrust earthquakes are among the strongest earthquakes in the world and occur in zones of subduction, where two tectonic plates converge and one slides under the other. The plates continuously move towards each other, but if the interface, or the defect, between them is stuck, then a slip deficit builds up over time. Like a debt, this shortfall must eventually be paid off, and for tectonic plates, payday is earthquake day. When these earthquakes affect the shallower part of the fault near the seabed, they have the potential to move the seabed upward and also create devastating tsunamis.
Understanding the potential failure behavior of megathrusts, particularly in the shallow offshore portion of the fault where the most destructive tsunamis are generated, is therefore a critical task for geoscientists who predict the risks of seismic and tsunami flooding. The likelihood of seismic behavior is often assumed to be somewhat low in the shallow end of the fault, based on laboratory studies of the material from the recovered fault zone.
The slip deficit accumulation rate of the fault can also be measured through the use of geodetic observations that track how the earth’s surface moves over time, for example by using very GPS sensors. accurate settled on the earth, as well as a model that tells how the slip on the fault. affects the movement of these stations. However, it is difficult for scientists to use this technique to “see” what is going on in the shallower part of the fault because it is far from the earth, under miles of water, where the instruments Traditional GPS cannot work.
Now, scientists from the University of New Mexico and the Nanyang Technological University (NTU) in Singapore have developed a new geodesic method to deduce this value which takes into account the interaction between the different parts of the fault, which gives a much more precise result physically. Lindsey’s team noted that previous models failed to take into account that if the deep end of the fault gets stuck between earthquakes, the shallow end can’t move either – that’s in what they call a “ stress shadow ” and there is no energy buildup available to drag it around. Taking this effect into account, the team developed a technique that uses the same terrestrial data but results in a great improvement in their ability to “see” fault slip in areas farthest from the shore, allowing researchers to reassess the danger presented by the offshore parts of the subduction zones most prone to the generation of tsunamis.
“We applied this technique to the Cascadia and Japan subduction zones and found that wherever deeper locked patches are present, the shallow fault must also have a high slip deficit – regardless of its own frictional properties. said Eric Lindsey, assistant professor in the Department of Earth and Planetary Sciences at UNM who conducted the research at the Singapore Earth Observatory at NTU. “If these areas can slide seismically, the risk of a global tsunami could be higher than what is currently recognized. Our method identifies critical places where seabed observations could provide information on the friction properties of these faults. in order to better understand their sliding behavior. “
This study is important because it calls for a reassessment of previous models of tsunami risk on megathrusts around the world. As can be done with existing data, reassessment can also be done relatively quickly. Hopefully this will lead to better preparation of coastal communities for future events.
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Material provided by University of New Mexico. Original written by Steve Carr. Note: Content can be changed for style and length.