Faulting in Deforming Natural Lherzolite at High Pressure and Temperature: Implications for Intermediate-Depth Earthquakes Generation in the Lower Seismic Zone
Description:
Intermediate-depth earthquakes (IDEQs), occurring at ~50-300 km depths, often form a double seismic zone along subducting slabs. The origin of these earthquakes has been in debate for decades, as rocks are expected to deform plastically under the high pressure (P) and temperature (T) conditions in the Earth’s interior rather than faulting. For many years, the cause of IDEQs has been attributed to the dehydration-triggered embrittlement. However, for earthquakes in the lower seismic zone (LSZ), which lies ~10-50 km below the slab surface within the oceanic lithospheric mantle, the hydrous minerals required for the dehydration mechanism may not be present.
In this study, we performed deformation experiments coupled with acoustic emission (AE) monitoring on a natural lherzolite, one of the major constituent rocks of the LSZ in oceanic lithospheric mantle. The natural lherzolite sample was collected from Western Alps (kindly provided by Drs. Julien Gasc and Alexandre Schubnel from Laboratoire de Géologie, CNRS UMR 8538, École Normale Supérieure, PSL University), providing realistic lithology for testing the physical mechanisms of earthquakes in the LSZ. The experiments were performed at GSECARS beamlines at the Advanced Photon Source (APS), using DDIA and DDIA-30 (a large version of DDIA with a double-stage configuration) deformation apparatus, coupled with synchrotron monochromatic X-ray diffraction for stress measurements, radiographic imaging for strain measurements and in-situ AE monitoring using PZT transducers attached to the back of each anvil. The experiments were performed at confining pressures of 3-5 GPa, temperatures from 500 to 1200°C, and strain rates of ~10-5 s-1. AE activities and faulting in the sample were observed in the temperature range from ~600 to 1000°C, whereas below ~600°C and above ~1000°C, the sample was ductile. We will present detailed experimental results and microstructural analyses of the recovered samples, as well as the implications of the new results to our further understanding of the triggering mechanisms of intermediate-depth earthquakes.
Session: Structure and Properties of Subducting Slabs and Deep Earthquakes [Poster]
Type: Poster
Date: 4/19/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Man Xu
Student Presenter: No
Invited Presentation:
Authors
Man Xu Presenting Author Corresponding Author mxu@cars.uchicago.edu University of Chicago |
Timothy Officer officer@cars.uchicago.edu University of Chicago |
Tony Yu tyu@cars.uchicago.edu University of Chicago |
Yanbin Wang wang@cars.uchicago.edu University of Chicago |
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Faulting in Deforming Natural Lherzolite at High Pressure and Temperature: Implications for Intermediate-Depth Earthquakes Generation in the Lower Seismic Zone
Category
Structure and Properties of Subducting Slabs and Deep Earthquakes