Dec. 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.)

Nov. 7 2024- Diego Molina - (ISTerre, Grenoble, 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.)

Oct. 3rd 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.

Sept 5th 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, from Instituto Geofísico, Escuela Politécnica Nacional, Ecuador, on 15 years of active tectonics in Ecuador and perspectives.
– Laurence Audin, from ISTerre, France, on 15 years of active tectonics in Ecuador and perspectives.
– Hans Agurto-Detzel, from KIT, Germany, on 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 and Jean-Paul Ampuero who will present the IRN-Andes-FRENSZ initiative
– Anaïs Férot who will present the NSF-sponsored SZ4D initiative and its related SZNet component

March 7 2024 - Subduction zones : Across scales

– Emilie Klein, from ENS Paris, who will talk about "Slip modes in the Atacama segment of the Chilean Subduction zone"
– Andres Tassara, from the University of Concepción, Chile, who will present on Thermal control on megathrust seismicity along the Chilean margin