Why do subduction zones have deep earthquakes

These hazards affect millions of people around the world, particularly around the edges of the Pacific Ocean, which mainly consist of subduction zones. The largest earthquakes on Earth occur at the interface between the two plates, called the megathrust. Recent examples include the magnitude 8. Earthquakes are caused by movement over an area of the plate interface called the seismogenic zone. It is then released catastrophically in one or more earthquakes. Above and below this area on the fault, stress cannot build up, and the movement between the plates occurs relatively smoothly through time, and thus does not produce large earthquakes.

An important implication of this is that the updip limit of the earthquake rupture zone should be viewed in terms of dynamic processes that operate at high slip rates, rather than the change from velocity-weakening to velocity-strengthening frictional behavior Figure These features suggest that fluidization may be caused by the restraint of a temperature rise by thermal pressurization.

In the Shimanto accretionary complex, the thickness of the fluidized zones is typically a few centimeters, which is 1 order of magnitude thicker than that of molten zones. In contrast to frictional melting, it is probable that fluid does not escape from the slipping zone during earthquake faulting, which results in thermal pressurization-induced fluidization. In addition to transport properties such as permeability, the thickness of the seismic slip zone appears to be an important factor controlling coseismic deformation mechanisms.

The estimated viscosity and apparent coefficient of friction or shear stress during fluidization are very low, showing that fluidization is also a dynamic weakening mechanism of faults during subduction earthquakes. The fluid-rock interaction recorded in fault zones of exhumed accretionary complexes has been mostly interpreted in terms of a seismic cycle or coseismic fluid-rock interactions.

Geological and experimental investigations of subduction zone rocks suggest that fluid plays a key role in slow slip processes in subduction zones, which is consistent with the results of geophysical measurements. However, there has been limited research in this area, and future study is required to examine the frictional properties of various lithologies in subduction zones. On-land accretionary complexes and metamorphic rocks exhumed from source depths of slow earthquakes are expected to record the slow slip processes in subduction zones.

Future geological studies are required to shed light on slow earthquakes. Finally, multi-disciplinary and integrated approaches are crucial to gain a better understanding of the dynamics and physico-chemical processes operating during earthquakes in subduction zones. They include investigations of fault rocks in accretionary prisms, laboratory experiments using subduction zone materials, numerical modeling incorporating the results of fault rock studies and laboratory measurements, geophysical surveys in subduction zones, and sampling and monitoring of active fault zones by deep-ocean drilling.

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London, Special Publication: The nature and tectonic significance of fault zone weakening, vol , Geological Society; — Download references. We would like to thank all of our collaborators for their insightful and thoughtful discussions. We owe thanks to Arito Sakaguchi and Asuka Yamaguchi for providing original graphics in Figures 6 and 7 , respectively; to Francesca Meneghini for original photomicrographs in Figures 10 f, 12 b, and c; Christie Rowe for an original outcrop photo in Figure 12 a; Jun Kameda and Tsuyoshi Ishikawa for original graphics in Figures 13 b and 15 , respectively; and to Ake Fagereng for original photos and graphics in Figure We thank two anonymous reviewers, Francesca Meneghini, and Casey Moore for their helpful comments and editing.

You can also search for this author in PubMed Google Scholar. Correspondence to Kohtaro Ujiie. KU and GK wrote the manuscript and prepared the figures. KU carried out the experimental and microstructural studies. Both authors read and approved the final manuscript.

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Skip to main content. Search all SpringerOpen articles Search. Download PDF. Abstract Subduction earthquakes on plate-boundary megathrusts accommodate most of the global seismic moment release, frequently resulting in devastating damage by ground shaking and tsunamis. Figure 1. Full size image. Figure 2. Figure 3. Intermediate depth quakes have long been something of a mystery to geologists.

Story Source: Materials provided by Brown University. Dehydration of lawsonite could directly trigger earthquakes in subducting oceanic crust. Nature , ; : 81 DOI: ScienceDaily, 3 February Brown University. Research may explain mysterious deep earthquakes in subduction zones.

Retrieved November 12, from www. A new study has found that when underwater mountains The sinking of one plate beneath another causes volcanism and earthquakes.

Scientists have been able to drill and investigate But the probability of such earthquakes does not appear to be ScienceDaily shares links with sites in the TrendMD network and earns revenue from third-party advertisers, where indicated. Print Email Share.