Work

Lower‐Crustal Earthquakes: Strain Rate Controls the Magnitude and Rate of Stress Amplification in Rigid Blocks

Year: 2025

Type: article

Abstract: Earthquakes in the dry lower continental crust are enigmatic, as they require very high deviatoric stresses. Field observations suggest that stress amplification in rigid blocks surrounded by ductile shear zones leads to seismic failure: the jostling block model. Here we quantify this model by systematically testing numerically how variations in geometry, material properties, and loading conditions impact magnitude and rate of stress amplification. We demonstrate that bulk strain rate is the dominant factor controlling stress amplification. High strain rates of 10 −10 –10 −12 s −1 cause stresses on the 10 2 –10 3 –MPa level within 10 0 –10 2 years, while lower strain rates are insufficient to generate the stresses required for lower‐crustal earthquakes. While geometries and material properties play a subordinate role in causing stress amplification, tests with varying loading conditions show that pure shear is more effective in generating high stress amplifications compared to simple shear in the case of the given geometry.

Source: Geophysical Research Letters

DOI: 10.1029/2024gl114350

Authors: Sascha Zertani, Marcel Thielmann, Luca Menegon

Institutions: University of Oslo, University of Bayreuth

Language: English

Topic: earthquake and tectonic studies

Subfield: Geophysics

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,190

Funders: Deutsche Forschungsgemeinschaft, Norges Forskningsråd