Full Source Characterization of the M5.4 11 November 2019 Le Teil, France Earthquake Based on a Multi-Technology Approach

Session: Earthquake Source Parameters: Theory, Observations and Interpretations [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The ML5.4 Le Teil, France earthquake that occurred on 11 November 2019 is of particular interest because 1) it is the largest earthquake recorded in France in the last 16 years, 2) it happened in a country with sparse historical and instrumental seismicity and 3) it was recorded by several technologies (seismic, satellite, infrasound). The last regional earthquake with a larger magnitude (M6.2) was the Lambesc event in 1909, about 110 km away. The Le Teil event, therefore, offers a rare opportunity to combine different approaches to fully characterize its seismic source and, more generally, the regional crustal deformation.

The focal mechanism determined from the full waveform inversion of long-period seismic data (RESIF and CEA) is consistent with the activation of a reverse fault with a strike around 45N and is associated with a moment magnitude Mw 4.8.

Moreover, this event provides a new minimum in terms of seismically induced infrasound amplitude. It is indeed the smallest event ever recorded by infrasound measurements at ~110 km away. Analysis of the infrasound waves indicates an azimuth of atmospheric propagation corresponding to the actual epicenter.

Furthermore, despite the moderate magnitude of the event, ground deformation is resolved by InSAR and agrees with the shallow source depth inverted from seismology. The inversion of multiple InSAR tracks helps constrain the displacement on the fault plane, and confirms the focal mechanism derived from seismology. The 2019/11/11 earthquake ruptured a 5-km long by ~1.5-km deep fault. The maximum slip is located around 1 km depth.

By comparing these results with known local geology and inherited regional structural features, the source coincides with the Rouvière fault. This fault belongs to the Cévennes fault system and was formerly known as a normal fault. This reverse earthquake is an example of an inherited structure re-activation as it is often the case in intraplate regions with polyphased history.

Presenting Author: Aurelie Guilhem Trilla

Authors