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WITHDRAWN Fast Crustal Slip Rates (Vertical and Horizontal) Revealed by Lidar Derived Topography Above the Subducted Chile Ridge, Patagonia

Description: 

W/D The effect of an oceanic ridge spreading center being subducted on the overlying plate is poorly known and Chilean Patagonia is the perfect natural laboratory to evaluate this. At the Laguna San Rafael (~47 degrees Latitude South) in Chile's Aysen Region, we designed and collected a novel airborne light detection and ranging (lidar)-derived topographic models and drone photography-derived structure from motion (SfM) models, supported by field observations to map Quaternary deposits and bedrock geology displaced along the dominantly strike slip Liquiñe-Ofqui fault zone (LOFZ). The LOFZ accomodates oblique subduction here, is the limit of the Chiloe Microplate, and appears to control the surface location of volcanoes in the southern 600 km of the Southern Volcanic Zone, i.e. volcanic arc in Patagonia. The LOFZ is seismogenic and responsible for a damaging and fatal Mw 6.2 earthquake in 2007 that occured along a minor fault that intersects with the master fault. Dated glacier deposits, from the most equatorial glacier on Earth, the well-studied San Rafael, when combined with displacements we measured in the models and verified in the field, yield horizontal slip rates of 13.8 ± 4.9 and 14.1 ± 1.0 mm/yr. Holocene vertical rates are the fastest on Earth, ~6 ± 3 mm/yr, and these vertical rates are apparent in satelite observations nearby but outside of the lidar-swath (and at correspondingly lower resolution. Fault traces found in the tectonic geomorphology were traced to natural exposures of fault rocks which show a flower structure forming during transpression. Because the dip slip along the LOFZ is ~0 mm/yr 750 km to the north, the rapid neotectonic uplift here along the LOFZ is likely controlled by oblique subduction of the Chile Ridge and associated slab window, and contributes to some of the highest topography found in Patagonia (~4 km). These field data confirm seismic observations and geodetic models that suggest fast slip rates along the LOFZ here, and provide important insight into the seismic hazard in Patagonia as the master fault did not rupture in 2007, it presents a major source of seismic hazard.

Session: From Earthquakes to Plate Boundaries: Insights Into Fault Behavior Spanning Seconds to Millennia

Type: Oral

Date: 4/20/2023

Presentation Time: 02:15 PM (local time)

Presenting Author: Gregory P. De Pascale

Student Presenter: No

Invited Presentation: 

Authors