loading page

Variable Slip Modes in Postseismic Deformation North of the April 16, 2016 Mw 7.8 Pedernales, Ecuador Megathrust Earthquake
  • +14
  • Mariah Chambers Hoskins,
  • Anne Meltzer,
  • Lillian Soto-Cordero,
  • Josh Stachnik,
  • Susan L. Beck,
  • Colton Lynner,
  • Mario Calizto Ruiz,
  • Alexandra Patricia Alvarado,
  • Stephen Hernandez,
  • Philippe Charvis,
  • Yvonne Font,
  • Jean-Mathieu Nocquet,
  • Frederique Rolandone,
  • Marc M Regnier,
  • Hans Agurto-Detzel,
  • Sergio Leon Rios,
  • Andreas Rietbrock
Mariah Chambers Hoskins
Lehigh University

Corresponding Author:mac716@lehigh.edu

Author Profile
Anne Meltzer
Lehigh University
Author Profile
Lillian Soto-Cordero
Lehigh University
Author Profile
Josh Stachnik
Lehigh Univeristy
Author Profile
Susan L. Beck
University of Arizona
Author Profile
Colton Lynner
University of Arizona
Author Profile
Mario Calizto Ruiz
Instituto Geofísico, Escuela Politécnica Nacional
Author Profile
Alexandra Patricia Alvarado
Instituto Geofísico, Escuela Politécnica Nacional
Author Profile
Stephen Hernandez
Instituto Geofísico, Escuela Politécnica Nacional
Author Profile
Philippe Charvis
Géoazur - Université Nice Sophia Antipolis Université Côte d'Azur, IRD, CNRS, OCA
Author Profile
Yvonne Font
Université Côte d'Azur, IRD, CNRS, Géoazur
Author Profile
Jean-Mathieu Nocquet
Géoazur - Université Nice Sophia Antipolis
Author Profile
Frederique Rolandone
Institut de Recherche pour le Développement - IRD
Author Profile
Marc M Regnier
Géoazur - Université Nice Sophia Antipolis Université Côte d'Azur, IRD, CNRS, OCA
Author Profile
Hans Agurto-Detzel
Géoazur - Université Nice Sophia Antipolis
Author Profile
Sergio Leon Rios
University of Liverpool
Author Profile
Andreas Rietbrock
University of Liverpool
Author Profile

Abstract

The north Ecuador subduction zone has a history of experiencing a range of slip modes including megathrust and other fast slip, slow, and aseismic slip. In 1906, a Mw 8.8 megathrust ruptured 500 km along the north Ecuador/Colombia margin. Parts of this region re-ruptured in events (south to north): ‘42 (Mw 7.8), ‘58 (Mw 7.7), and ‘79 (Mw 8.2). The April 16, 2016 Pedernales megathrust rupture overlapped the ‘42 rupture. Postseismic deformation following the 2016 event exhibited a range of slip behaviors and associated seismicity. A dense temporary land and offshore deployment augmented permanent stations of the national network (RENSIG) to record postseismic deformation for one year. Aftershocks concentrate spatially in bands or clusters mirroring patterns in background seismicity marking persistent asperities which cause variations in plate coupling. Bands of aftershocks outline the 2016 rupture and two patches of larger slip within the rupture; additional bands are observed to the south and to the north. North of the rupture, bands and clusters are observed near Punta Galera, Atacames, and Esmeraldas. Seismicity near Punta Galera outlines the north edge of a patch of aseismic slip that occurred in the month following the mainshock. One month after the mainshock, Mw 6.7 and 6.9 aftershocks occurred. Calibrated relocations show these are interface events north of the 2016 rupture, downdip of the aseismic slip. On 7/11/ 2016, Mw 5.9 and 6.3 interface events occurred, causing an increase in local seismicity. In June intermittent seismicity began in Esmeraldas, near the 1958 rupture. An earthquake swarm and a transient in GPS data in July 2016 suggests possible slow slip in the region. Relocations of earthquakes in the swarm outline a splay fault in the upper plate. An increase in seismicity near Atacames in December suggests fast slip. Calibrated relocations of the 5 largest events (M 4.7-5.2) and automatic locations of the remaining 246 events show they are upper plate events. In the months following the Pedernales event, fast, aseismic, and slow slip occur north of the rupture. Near Atacames and Esmeraldas upper plate seismicity is predominant.