Slow glides provide insight into earthquakes

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In the subduction zone where two tectonic plates collide, slow slip events or silent earthquakes can occur. Although these events do not pose a threat, they can trigger earthquakes nearby. credit: 2021 KAUST; Hino Hwang

Large earthquakes, from mild shaking to devastating tremors, are hazards caused by the sudden release of pressure that has built up in geological faults. More subtle events called slow slips are attracting increasing interest as are the undisturbed versions of the dramatic seismic fractures of the largest earthquakes.

KAUST and researchers from the University of Geneva compiled a database of information on past slow slides to develop a model for the mechanisms of these geological events, in collaboration with colleagues at ETH Zürich in Switzerland, GFZ in Germany, and the University of Bologna in Italy.

Slow slips, also known as silent earthquakes, are fractures in the Earth’s crust that propagate very slowly without producing seismic waves. They usually last over a few weeks or months, and their duration can range from less than a day to more than a year.

“Slow glides alone pose no threat because they do not generate vibration and therefore do not cause any damage or disruption to property, but they do cause disturbances that can lead to Regular earthquakes nearby.”

The possibility of regular earthquakes is one reason researchers are keen to learn more about slow-slide events. Another reason is that they come with small tremors or sometimes a wave of small earthquakes, the so-called seismic swarm, in a process that is not yet fully understood.

Slow-slide events occur in many areas where tectonic plates collide and slide but particularly in subduction zones around Japan, New Zealand, and North and Central America. They also occur near volcanoes such as Mt. Etna in Italy and Kilauea in Hawaii.

“We have compiled the first systematic catalog of the seismic and seismic properties of slow slip events to understand the physical mechanisms that generate both,” Passarelli says. He adds that this has been a major challenge because the data is not consistently archived or readily available.

The results allowed the team to assess the association between characteristics of each slow event and evoked tremor activity, in terms of magnitude and duration, and potential immediate and potential long-term consequences. This information can now be used to improve a model to predict the changes and risks associated with certain types of events.

“We have taken a step towards a better understanding of the processes that control slow slip and seismic tremors, although there is more to investigate,” Passarelli says. The researchers hope that their database and modeling can be further developed to build a better understanding of these complex processes.

The hidden mechanics of slow-slip seismicity has revealed more information: Luigi Passarelli et al., Scale of source and seismic productivity of slow-slide seismicity, Science Advances (2021). DOI: 10.1126 / sciadv.abg9718 Submitted by King Abdullah University of Science and Technology

Quote: Slow slips provide insights into earthquakes (2021, Aug 5) Retrieved Aug 6, 2021 from https://phys.org/news/2021-08-insights-earthquakes.html

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