← Back to Sessions

Imaging the Taltal Segment in Northern Chile: Tectonic Implications Inferred from Seismicity Distribution, Local Earthquake Tomography and Moment Tensor Calculations

Description: 

Northern Chile sets an ideal laboratory to perform seismic experiments and collect high-quality data to better understand the subduction process in highly erosive margins. In terms of tectonics, the setting is mainly driven by the convergent margin where the Nazca plate subducts beneath the South American plate. In particular, the Taltal segment between ~22°S and ~26°S has been the subject of notable scientific attention; however, the previous studies have put their focus mainly on the coastal areas affected by large earthquakes during the past 30 years, leaving unattended the processes in the overriding plate from the coastline to the volcanic arc.

By benefiting from a large temporary deployment with 84 short-period geophones and the high rate of seismicity in the region, we tectonically characterize the Taltal segment by deriving regional 3D Vp, Vs, and Vp/Vs velocity models together with a seismic catalog with 23,000 earthquakes and regional moment tensors for the events with M> 4.0.

Vp and Vs models illuminate first-order structures such as the Nazca plate with a Vp~ 7-8 km/s, Vs~4-5 km/s anomaly dipping eastward; and the upper crust of the South American plate with values of Vp~ 5-7 km/s and Vs~ 3-4 km/s. Vp/Vs model highlights changes from high to low ratios in the overriding plate that collocate with large-scale structures such as the Atacama fault system (AFS) in the coastline and the West Fault System (WFS) towards the Andes.

The distribution of seismicity is mainly located along the plates interface between 20-150 km depth; however, we observe a dip change at intermediate depths (150 - 200 km) that could be related to the slab-pull activity. We also identify clustered seismicity at the coast that might be associated with splay faults reaching down to the plate interface. Finally, upper-crust activity is mainly related to the active AFS and WFS but also to the circulation of fluids around the Lascar volcano.

Session: Subduction Zone Structure From Trench to Arc

Type: Oral

Date: 4/19/2023

Presentation Time: 08:45 AM (local time)

Presenting Author: Sergio Leon-Rios

Student Presenter: No

Invited Presentation: 

Authors