Academic Commons

Articles

A narrowly spaced double-seismic zone in the subducting Nazca plate

Rietbrock, A.; Waldhauser, Felix

High-precision relocations of intermediate-depth earthquakes (80–130 km) below the Central Andes reveal a fine-scale double-layered Wadati-Benioff zone (WBZ). Upper and lower band of seismicity are separated by about 9 km and occur at the top of the oceanic crust and in the uppermost oceanic mantle, respectively. Analysis of focal mechanisms and waveform similarities indicate that fluid processes are causing the events. Earthquakes in the oceanic crust occur on pre-existing normal faults due to hydraulic embrittlement from metamorphic dehydration, and on subvertical faults that connect the two layers in a narrow depth range. Extensional faulting predominates in both layers, indicating that slab pull forces are the dominant stress source superseding possible unbending forces in this segment of the Nazca plate.

Geographic Areas

Subjects

Files

Also Published In

Title
Geophysical Research Letters
DOI
https://doi.org/10.1029/2004GL019610

More About This Work

Academic Units
Lamont-Doherty Earth Observatory
Published Here
May 5, 2014
Academic Commons provides global access to research and scholarship produced at Columbia University, Barnard College, Teachers College, Union Theological Seminary and Jewish Theological Seminary. Academic Commons is managed by the Columbia University Libraries.