TY - JOUR
T1 - 1D-velocity structure and seismotectonics of the Ecuadorian margin inferred from the 2016 Mw7.8 Pedernales aftershock sequence
AU - León-Ríos, Sergio
AU - Agurto-Detzel, Hans
AU - Rietbrock, Andreas
AU - Alvarado, Alexandra
AU - Beck, S.
AU - Charvis, Phillipe
AU - Edwards, Benjamin
AU - Font, Yvonne
AU - Garth, Tom
AU - Hoskins, Mariah
AU - Lynner, Colton
AU - Meltzer, Anne
AU - Nocquet, Jean Matthieu
AU - Regnier, Marc
AU - Rolandone, Frederique
AU - Ruiz, M.
AU - Soto-Cordero, Lillian
N1 - Funding Information:
This study was supported by IGEPN , IRD , the INSU,CNRS and the ANR grant ANR-15-CE04-0004 . The UK portion of the temporary deployment was supported by NERC grant NE/P008828/1 . The US portion of the temporary deployment was supported by IRIS PASSCAL and NSF RAPID Program Award EAR-1642498 . SLR acknowledges partial support from Programa Formacion de Capital Humano Avanzado, BECAS DE DOCTORADO EN EL EXTRANJERO, BECAS CHILE (Grant 8068/2015 ). HAD acknowledges support from ANR project ANR-15-CE04-0004 and UCA/JEDI project ANR-15-IDEX-01 .
Funding Information:
This study was supported by IGEPN, IRD, the INSU,CNRS and the ANR grant ANR-15-CE04-0004. The UK portion of the temporary deployment was supported by NERC grant NE/P008828/1. The US portion of the temporary deployment was supported by IRIS PASSCAL and NSF RAPID Program Award EAR-1642498. SLR acknowledges partial support from Programa Formacion de Capital Humano Avanzado, BECAS DE DOCTORADO EN EL EXTRANJERO, BECAS CHILE (Grant 8068/2015). HAD acknowledges support from ANR project ANR-15-CE04-0004 and UCA/JEDI project ANR-15-IDEX-01. We are also indebted to Ben Yates, Davide Oregioni and Deny Malengros from Geoazur laboratories, INOCAR, Comandante Andr?s Pazmino (INOCAR) and Captain Patricio Estupinian (Esmeraldas Coastguard) to operate OBSs at sea in very harsh environments. Authors want to thanks to all involved in the deployment and data collection for his invaluable collaboration with this study. Finally, to all the people in Ecuador who allowed us to install our stations in their houses, big thanks for your hospitality, patience and help when was needed.
Publisher Copyright:
© 2019
PY - 2019/9/20
Y1 - 2019/9/20
N2 - On April 16th 2016 a Mw 7.8 earthquake ruptured the central coastal segment of the Ecuadorian subduction zone. Shortly after the earthquake, the Instituto Geofisico de la Escuela Politecnica Nacional of Ecuador, together with several international institutions deployed a dense, temporary seismic network to accurately categorize the post-seismic aftershock sequence. Instrumentation included short-period and broadband sensors, along with Ocean Bottom Seismometers. This deployment complemented the permanent Ecuadorian seismic network and recorded the developing aftershock sequence for a period of one year following the main-shock. A subset of 345 events with ML > 3.5, were manually picked in the period of May to August 2016, providing highly accurate P- and S-onset times. From this catalogue, a high-quality dataset of 227 events, with an azimuthal gap <200°, are simultaneously inverted for, obtaining the minimum 1D velocity model for the rupture region, along with hypocentral locations and station corrections. We observe an average Vp/Vs of 1.82 throughout the study region, with relatively higher Vp/Vs values of 1.95 and 2.18 observed for the shallowest layers down to 7.5 km. The high relative Vp/Vs ratio (1.93) of the deeper section, between 30 km and 40 km, is attributed to dehydration and serpentinization processes. For the relocated seismicity distribution, clusters of events align perpendicular to the trench, and crustal seismicity is also evidenced, along with earthquakes located close to the trench axis. We also compute Regional Moment Tensors to analyze the different sources of seismicity after the mainshock. Aside from thrust events related to the subduction process, normal and strike-slip mechanisms are detected. We suggest that the presence of subducting seamounts coming from the Carnegie Ridge act as erosional agents, helping to create a scenario which promotes locking and allows seismicity to extend up to the trench, along zones of weakness activated after large earthquakes.
AB - On April 16th 2016 a Mw 7.8 earthquake ruptured the central coastal segment of the Ecuadorian subduction zone. Shortly after the earthquake, the Instituto Geofisico de la Escuela Politecnica Nacional of Ecuador, together with several international institutions deployed a dense, temporary seismic network to accurately categorize the post-seismic aftershock sequence. Instrumentation included short-period and broadband sensors, along with Ocean Bottom Seismometers. This deployment complemented the permanent Ecuadorian seismic network and recorded the developing aftershock sequence for a period of one year following the main-shock. A subset of 345 events with ML > 3.5, were manually picked in the period of May to August 2016, providing highly accurate P- and S-onset times. From this catalogue, a high-quality dataset of 227 events, with an azimuthal gap <200°, are simultaneously inverted for, obtaining the minimum 1D velocity model for the rupture region, along with hypocentral locations and station corrections. We observe an average Vp/Vs of 1.82 throughout the study region, with relatively higher Vp/Vs values of 1.95 and 2.18 observed for the shallowest layers down to 7.5 km. The high relative Vp/Vs ratio (1.93) of the deeper section, between 30 km and 40 km, is attributed to dehydration and serpentinization processes. For the relocated seismicity distribution, clusters of events align perpendicular to the trench, and crustal seismicity is also evidenced, along with earthquakes located close to the trench axis. We also compute Regional Moment Tensors to analyze the different sources of seismicity after the mainshock. Aside from thrust events related to the subduction process, normal and strike-slip mechanisms are detected. We suggest that the presence of subducting seamounts coming from the Carnegie Ridge act as erosional agents, helping to create a scenario which promotes locking and allows seismicity to extend up to the trench, along zones of weakness activated after large earthquakes.
KW - 2016 Pedernales earthquake
KW - Aftershock sequence
KW - Ecuador
KW - Regional moment tensor
KW - Subduction zone
KW - Velocity model
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U2 - 10.1016/j.tecto.2019.228165
DO - 10.1016/j.tecto.2019.228165
M3 - Article
AN - SCOPUS:85069874940
VL - 767
JO - Tectonophysics
JF - Tectonophysics
SN - 0040-1951
M1 - 228165
ER -