June 5, 2025
► Yida Li, FAST laboratory, France
“Large-Scale Slab Dynamics as Drivers of Seismicity : Modeling Earthquakes in the Izu-Bonin-Mariana Subduction Zones”
► Sergio Ruiz, Universidad de Chile
“Heterogeneous Seismic Behavior on the Megathrust along the Chilean Subduction Zone”
May 6 2025
► Joaquín Julve, Cardiff University, UK
“Geological Controls on the Seismic Cycle of Megathrust Earthquakes : Insights from Numerical Modelling and the Chilean Subduction Zone”
The Chilean subduction zone, host to some of the largest earthquakes ever recorded, has experienced several major seismic events in recent decades. These events have led to improved data acquisition and significant advances in slip characterization. However, the fundamental controls governing earthquake nucleation and seismic behaviour remain poorly understood. This presents an opportunity to integrate geological and geophysical observations into physics-based numerical models. We use quasi-dynamic simulations to investigate how forearc geological structure and fluid distribution along the megathrust influence the nucleation, size, and recurrence of simulated earthquakes. Our results demonstrate that the interseismic phase is not mechanically static. Even under nominally homogeneous boundary conditions, shear stress evolves heterogeneously over time, leading to temporally variable slip rates. These findings highlight the critical role of the geological and fluid distribution in shaping the seismic cycle at subduction zones.
► Caroline Chalumeau, ISTerre, France
“The Maule seismic sequence revisited : insights into the fine-scale structure of the deep subduction interface”
April 4 2025
►Sylvain Michel, Géoazur, France
“14 Years of Slip History of the Hikurangi Subduction Zone”
►Whitney Behr, ETH Zurich, Switzerland
“The role of interface rheology on large-scale subduction dynamics : constraints from the field, the lab, and numerical models”
March 3 2025
►Laura Wallace - Geomar, GNS
“Near-Trench megathrust slip processes from a decade of seafloor geodetic observations at the Hikurangi subduction zone, New Zealand”
Resolving the distribution of transient slow slip event (SSE) and interseismic coupling processes at offshore subduction zones is hampered by the difficulty of measuring offshore crustal deformation. Four methods are overcoming these challenges : (1) GNSS-Acoustic techniques to track the horizontal motion of the seafloor ; (2) ocean bottom pressure sensors to discern cm-level seafloor pressure changes due to vertical deformation, (3) formation pore pressure changes in subseafloor IODP observatories as a proxy for formation volumetric strain, and (4) direct-path acoustic measurements to resolve mm-level changes in baseline length over short (a few km) baselines. All of these approaches have been employed (concurrently with deployment of ocean bottom seismometers) in several experiments over the last decade along the Hikurangi subduction zone offshore New Zealand, with the goal of capturing near-trench slip behavior and its relationship to seismicity. I will present new insights into shallow megathrust slip behavior (transient deformation and interseismic coupling) from the diverse array of seafloor geodetic deployments undertaken offshore New Zealand over the last decade. I will also discuss the integration of our seafloor geodetic observations with those from seismic imaging and scientific ocean drilling to help resolve the physical processes that influence subduction megathrust slip behavior.
February 13 2025
►Paul Jarrin - Géoazur
“Kinematics of the Northern Andes from GNSS observations"
January 16 2025
►Caroline François-Holden, Seismocity, New-Zealand
“Kinematics of the Northern Andes from GNSS observations"
December 5 2024
►Constanza Rodriguez-Piceda,U. of Plymouth, UK
“The signature of lithospheric strength on seismicity in the Central Andes”
In the southern Central Andes (29°S-39°S), the oceanic plate changes the subduction angle between 33°S and 35°S from almost horizontal (< 5° dip) in the north to a steeper angle ( 30° dip) in the south. This region displays remarkable along- and across- strike variations of the tectonic deformation patterns. I will talk about the effects of the long-term yield strength of the lithosphere on the active seismic deformation of the subduction zone bordering this sector of the Andes. By using multiple geophysical approaches and data sources, we constructed the structural, density, thermal and rheological 3D models of the lithosphere. We found that most of the seismicity within the continental plate occurs above the modelled transition from brittle to ductile conditions. In addition, upper-plate seismic deformation spatially correlates with the steepest strength gradients. Our work shows that thermomechanical conditions of the lithosphere could be a key factor influencing seismic deformation in the area.)
November 7 2024
► Diego Molina, ISTerre, France
“Numerical modelling and geodetic observations improving our understanding about seismic barriers"
Understanding what controls the maximum size of an earthquake is essential to estimate seismic hazard. Typically, zones promoting seismic rupture arrest along subduction megathrusts have been correlated with the subduction of bathymetric anomalies. They are often characterised by intermediate-low coupling, however the mechanisms producing such feature are poorly understood. To better understand potential frictional regime governing barrier behaviour, we perform numerical modelling simulations of the seismic cycle. We also recur to geodetic data to constrain how seismic barrier behaves in nature. Our results suggest that seismic barriers can display both Velocity weakening or Velocity strengthening regime. Posible mechanisms controlling the different frictional behaviour might be associated to subducting topography which provoke fault heterogeneities.
Finally, our study supports that geological characteristics of subducting and overriding plates can impact fault behaviour.)
October 3 2024
► Bar Oryan, Scripps UCSD, USA
“Megathrust locking encoded in subduction landscapes"
Locked areas of subduction megathrusts are increasingly found to coincide with landscape features sculpted over hundreds of thousand years, yet the mechanisms that underlie such correlations remain elusive. We show that interseismic locking gradients induce increments of irreversible strain across the overriding plate manifested predominantly as distributed seismicity. Summing these increments over hundreds of earthquake cycles produces a spatially variable field of uplift representing the unbalance of co-, post-, and interseismic strain. This long-term uplift explains first-order geomorphological features of subduction zones such as the position of the continental erosive shelf break, the distribution of marine terraces and peninsulas, and the profile of forearc rivers. Inelastic yielding of the forearc thus encodes short-term locking patterns in subduction landscapes, hinting that megathrust locking is stable over multiple earthquake cycles and highlighting the role geomorphology can play in constraining Earth’s greatest source of seismic hazard.
September 5 2024
► German Prieto, Geosciences Department, Universidad Nacional de Colombia
“Subduction initiation and what drives subduction in NW South America"
June 6 2024
Active tectonics and subduction processes in Ecuador
► Alexandra Alvarado, Instituto Geofísico, Escuela Politécnica Nacional, Ecuador
"15 years of active tectonics in Ecuador and perspectives"
► Laurence Audin, ISTerre, France
"15 years of active tectonics in Ecuador and perspectives"
► Hans Agurto-Detzel, from KIT, Germany
"Overview of the Ecuadorian subduction zone from a seismological point of view"
April 4 2024
Presentation of Andes-FrenSZ IRN and SZ4D initiative
► Mathilde Radiguet, ISTerre, France & Jean-Paul Ampuero, Géoazur, France
"IRN-Andes-FRENSZ initiative"
► Anaïs Férot, SZ4D, USA
"NSF-sponsored SZ4D initiative and its related SZNet component"
March 7 2024
Subduction zones : Across scales
► Emilie Klein, ENS Paris, France
"Slip modes in the Atacama segment of the Chilean Subduction zone"
► Andres Tassara, University of Concepción, Chile
"Thermal control on megathrust seismicity along the Chilean margin"
