Natural hazards (giant subduction zone thrust earthquakes)

3.1. Giant subduction zone megathrust earthquakes

Subduction zones produce the biggest and most destructive earthquakes (and related tsunami) on Earth. Indeed, the eight biggest earthquakes in recorded history (which is since 1900) are all subduction zone megathrust earthquakes, which occur at the plate boundary interface between the downgoing plate and overriding plate. Recent examples include the December 2004 Sumatra-Andaman earthquake and March 2011 Japan earthquake. Therefore, there is both a scientific and societal need to increase our understanding of subduction zone processes. In our group, we investigate, amongst other questions, why some subduction zones have produced giant subduction zone megathrust earthquakes, and why others have not. We use global subduction zone data, results from geodynamic models, seismic data and statistical investigations to address the above and other questions.

Main topics of research:

The physical and chemical characterization of subduction zones and how subduction parameters correlate with giant earthquakes (example)
Thermal dehydration coupled to high-pressure fluids in subduction zones
Mineral composition within subduction zones
Investigating the spatial and temporal distribution of giant subduction earthquakes (e.g. subduction zone earthquake hazard map)
The earthquake cycle in subduction zones: Foreshocks, mainshock and aftershocks

3.2 Volcanic eruptions
Volcanic eruptions and seismicity are closely intertwined, particularly in regions along subduction zones. In Japan, a country located along the Pacific Ring of Fire, the Pacific and Philippine plates subduct beneath the Okhotsk and Eurasian plates at rates of 8-9 cm/year and 5-6 cm/year, respectively. This tectonic movement generates intense seismic activity, including frequent earthquakes and volcanic eruptions. Volcanic activity, such as that observed at Mount Aso in southern Japan, is often triggered by the movement of magma towards the surface, which can be facilitated by the fracturing of rocks during earthquakes. The Kumamoto earthquake sequence of 2016, which included a mainshock of Mw 7.0, exemplifies this interaction. Besides Japan, notable eruptions include the 1980 eruption of Mount St. Helens in the United States, which was triggered by a massive landslide that uncapped the volcano's magma chamber, leading to a violent explosion and widespread ashfall. In Indonesia, the 1883 eruption of Krakatoa was one of the deadliest in recorded history, producing colossal tsunami and significantly impacting global climate. Similarly, the 2010 eruption of Eyjafjallajökull in Iceland highlighted the far-reaching effects of volcanic activity, as its ash plume disrupted air travel across Europe for weeks. Each of these eruptions is associated with complex tectonic settings, such as subduction zones or rift zones, where the movement of tectonic plates generates the necessary conditions for magma to rise to the surface.

Main topics of research:

Impact of earthquake-induced fracturing on magma ascent and volcanic Activity
Hydrothermal and geochemical changes due to seismic and volcanic activity
Long-term monitoring and modelling of seismic-volcanic interactions
Influence of volcanic eruptions on geothermal energy potential

Natural hazards (giant subduction zone thrust earthquakes)

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