← Back to Sessions

Comparison of Seismicity Along the Northern and Southern Central Andes and Its Relationship With Along-strike Variations in Andean Deformation

Description: 

Two dense arrays of nodal and broadband seismometers were deployed at ~23˚-24˚S and ~35˚-36˚S covering from the coast of Chile to the foreland in Argentina to understand the driving processes for the along-strike variations in deformation in the Andes. These two datasets are used to build an earthquake catalog for each of those two regions with a machine-learning-based workflow. Both the catalogs show abundant seismicity along the subducting Nazca slab, but the number of events observed at 23˚-24˚S is much higher compared to 35˚-36˚S. Both of these regions show a distinct cluster of events at ~80-120 km depth along the subducting Nazca slab, likely due to dehydration reactions. However, an additional cluster of events is observed at ~180-220 km depth at ~23˚-24˚S underneath the Puna plateau. Very few earthquakes are observed along the main volcanic arc and the Puna plateau at ~23˚S likely due to several factors such as the presence of the Altiplano-Puna magma body, elevated temperatures, and lower crustal flow. However, the main volcanic arc at ~35˚S shows abundant seismicity, which is mostly related to the volcanic unrest at the Laguna del Maule volcanic field, where a trans-crustal magma ascent process is observed. In the back-arc, abundant seismicity is observed along the fold-and-thrust belt at ~23˚-24˚S, where a detachment-involved deformation system is identified and it indicates active ongoing shortening, and also explains geologically inferred higher magnitude shortening at these latitudes. However, the back-arc at ~35˚-36˚S shows sparse low-magnitude seismicity in the Malargüe fold-and-thrust belt and Payenia volcanic field, indicating a nearly inactive thrust belt, potential volcanic influence on the seismicity, and also explains the overall low-magnitude shortening along these latitudes. The difference in these two catalogs reflects the variation in deformation processes that resulted in the along strike variations in the Andes.

Session: Linking Subduction Zone Processes and Cascading Hazards in Alaska, Cascadia, Chile and Beyond [Poster]

Type: Poster

Date: 4/16/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Sankha Subhra Mahanti

Student Presenter: Yes

Invited Presentation: 

Poster Number: 128

Authors