The federation
Intranet
Document the various ways faults slip
- Quantify slip rates on faults, especially by coupling tectonics, geodesy and seismology
- From present day deformation to cumulative deformation
- Relate present-day deformation to forcings
Correlation of optical satellite imagery and aerial photography provide a powerful method for retrieving the near-field deformation pattern produced during surface rupturing earthquakes. These measurements allow the pattern of surface slip to be characterized along-side parameters such as local geology, topography, structural complexity, soil thickness, and field-derived measurements of slip to see which parameters control the localization of slip at the surface (and the potential start and end points of ruptures). Due to the complexity in correlating various optical datasets, especially for historical satellite and aerial images, such comparisons are generally attempted on an event by event basis. Various papers addressing these questions have been published (Hollingsworth, et al., 2017 ; Kuo, et al., 2018 ; Socquet, et al. 2019 ; Zinke, et al., 2019). Generally, we have found that structurally mature fault systems feature more localized slip at the surface, while immature faults feature more diffuse off-fault deformation. Better understanding of these factors is critical for how we interpret spot measurements of earthquake slip history (from paleoseismic trenching), and quaternary fault slip rates in general ; both of which are critical ingredients into seismic hazard analysis.
Caption :
(a) East-west displacement map for the Kabateh and NW Zard Geli segments of the 1990 Rudbar earthquake, derived from correlation of 1955 and 2001-2003 aerial photos. (b) Left-lateral slip distribution along the Kabateh Segment, extracted from fault-perpendicular displacement profiles.
Our team has been involved :
– in the deployment of wide GNSS networks along the highly active South American - Nazca subduction zone, and in numerous collaborative GPS projects with South American researchers essentially from IGP Lima, IGEPN Quito and the DGF Santiago. These projects allowed to characterize the steady-state slip on the megathrust interface, and the motion of the Peruvian and Chilean Slivers, that are being accommodated by subandean fold and thrust faults in the Altiplano and nearby areas (Villegas Lanza et al., 2016 ; Métois et al. 2016). The high heterogeneity in the interplate coupling seen on the megathrust interface starts now to be relatively well known. Mapping the interseismic coupling on the megathrust interface appears essential to understand the variations of the frictional properties of the megathrust interface (Socquet et al. 2017 ; Marinière et al, 2020).
– in numerous projects to monitor the present-day deformation along Himalaya from Pakistan to Nepal. The occurrence of the Gorkha earthquake, the 25 April 2015, gives us the opportunity to document the postseismic deformation with the installation of permanent and episodic GNSS stations in key areas. These data allow us to conclude at the absence of afterslip along the Main Himalayan Thrust south of the rupture. Numerical simulations of afterslip taking into account the coseismic slip distribution allow to quantify relative contributions of afterslip along the MHT in the northern part of the rupture and viscous relaxation controlled by a narrow viscosity body (Jouanne et al., 2019). The geometry of this viscous body excludes the existence of a channel flow in central Himalaya.
