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Landscape Response to Deformation in the Northern Ecuadorian Forearc

Description: 

In the northern Ecuadorian forearc, subduction of the Nazca Plate and Carnegie Ridge beneath South America uplifts the Coastal Cordillera and activates faulting. This region has experienced multiple historic Mw 7.7–8.8 megathrust earthquakes, including the Mw 7.8 Pedernales earthquake in 2016, along with smaller (~M 5) crustal fault earthquakes. We use geomorphic metrics to analyze landscape response to long-term deformation and examine relationships with seismicity, slip behavior, and structure. Using the ALOS World 30m DEM dataset, we delineate drainage basins, generate long profiles to identify knickpoints, and calculate Normalized Steepness Index (Ksn), Hypsometric Integral, and Chi Analysis. We integrate these geomorphic metrics with earthquake locations and subsurface structure from a 3D tomographic inversion using local earthquake data recorded by dense broadband and nodal deployments. In the northern forearc, we delineate 89 drainage basins. Larger, older basins are inland, while smaller, younger basins are near the coast. Older drainages feature well-developed dendritic rivers, while younger basins do not, which reflects recent coastal uplift. Some rivers divert parallel to the coast before reaching the ocean. High Ksn values are noted along the Coastal Cordillera and main faults. The northern and southern segments of the Coastal Cordillera show westward drainage divide migration, while the central segment exhibits westward migration in the west and eastward migration in the east, connecting it to the southern segment. The seismicity has been plotted against the KSN values in our study area. Crustal seismicity of the Esmeraldas swarm has been previously correlated with an active fault. Knickpoints and high KSN values are found in the adjacent areas of the fault. The Rio Verde River intersects the Businga Dome, cored by mafic oceanic basalts. Changes in river sinuosity correlate with a crustal fault exhibiting slow-slip and earthquake swarms. We observe knickpoints associated with high KSN values on the surface above deep seismicity at the northeast downdip termination of the Pedernales rupture.

Session: The Landscape Record of Earthquakes and Faulting [Poster]

Type: Poster

Date: 4/16/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Michael

Student Presenter: Yes

Invited Presentation: 

Poster Number: 1

Authors