Calibration of subsurface dynamic parameters and fault geometry from surface fault rupture observations: an example from the shallow 2019 Mw4.9 Le Teil (France) event.

Sassi Rihab (1) , Hok Sébastien (1) , Klinger Yann (2) , Delouis Bertrand (3)

1 IRSN/PSE-ENV/SCAN/BERSSIN - Bureau d'évaluation des risques sismiques pour la sûreté des installations
2 IPG Paris - Institut de Physique du Globe de Paris
3 UniCA - Université Côte d'Azur

We investigate the impact of several friction, stress drop and fault geometry on surface fault rupture amount and patterns. Based on a shallow reverse surface rupturing Mw4.9 earthquake which occurred in southeastern France in November 2019, and models derived from data collected (InSAR, waveforms), we set up a rupture scenario that is consistent with the observations. From this kinematic scenario we constrain the dynamic parameters of the deeper part of the rupture (300-2 km depth), while we test the shallow part parameters (<300m). The surface rupture produced by the different models are then compared to the surface deformation patterns and amplitude. We show that the shallow surface layers are likely slip-strengthening, but also that the surface rupture is not a passive marker of the deeper rupture process: they are both linked. The frictional behavior (Dc, Stress drop, weakening or strengthening) directly modulates the amount of surface rupture. Dynamic rupture history notably differs from the kinematic model, although the friction evolution of the first was directly derived from the second. Adding a secondary structure in the northern part improves significantly the surface rupture fit, as well as the rupture history. Finally, such a shallow reverse fault earthquake seen through its dynamics emphasizes a puzzling question: what is the absolute level of stress on a seismogenic fault so close to the surface?

Domaines: Planète et Univers [physics]

Sassi Rihab, Hok Sébastien, Klinger Yann, Delouis Bertrand. Calibration of subsurface dynamic parameters and fault geometry from surface fault rupture observations: an example from the shallow 2019 Mw4.9 Le Teil (France) event.. SSA2022 - Seismological Society of America Annual Meeting, Apr 2022, Bellevue, United States. SEISMOLOGICAL SOCIETY OF AMERICA, SEISMOLOGICAL RESEARCH LETTERS, 93 (2B), pp.1308-1309, 2022, ⟨10.1785/0220220087⟩. ⟨hal-03914284⟩