1D-velocity structure and seismotectonics of the Ecuadorian margin inferred from the 2016 Mw7.8 Pedernales aftershock sequence

Sergio León-Ríos, Hans Agurto-Detzel, Andreas Rietbrock, Alexandra Alvarado, Susan Beck, Phillipe Charvis, Benjamin Edwards, Yvonne Font, Tom Garth, Mariah Hoskins, Colton Lynner, Anne Meltzer, Jean Matthieu Nocquet, Marc Regnier, Frederique Rolandone, M. Ruiz, Lillian Soto-Cordero

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish (US)
Article number228165
JournalTectonophysics
Volume767
DOIs
StatePublished - Sep 20 2019

Fingerprint

seismotectonics
velocity structure
aftershock
seismicity
margins
earthquakes
trench
earthquake
Ecuador
ocean bottom seismometer
seamounts
ocean bottom
moment tensor
serpentinization
seismographs
seamount
dehydration
thrust
locking
set theory

Keywords

  • 2016 Pedernales earthquake
  • Aftershock sequence
  • Ecuador
  • Regional moment tensor
  • Subduction zone
  • Velocity model

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes

Cite this

1D-velocity structure and seismotectonics of the Ecuadorian margin inferred from the 2016 Mw7.8 Pedernales aftershock sequence. / León-Ríos, Sergio; Agurto-Detzel, Hans; Rietbrock, Andreas; Alvarado, Alexandra; Beck, Susan; Charvis, Phillipe; Edwards, Benjamin; Font, Yvonne; Garth, Tom; Hoskins, Mariah; Lynner, Colton; Meltzer, Anne; Nocquet, Jean Matthieu; Regnier, Marc; Rolandone, Frederique; Ruiz, M.; Soto-Cordero, Lillian.

In: Tectonophysics, Vol. 767, 228165, 20.09.2019.

Research output: Contribution to journalArticle

León-Ríos, S, Agurto-Detzel, H, Rietbrock, A, Alvarado, A, Beck, S, Charvis, P, Edwards, B, Font, Y, Garth, T, Hoskins, M, Lynner, C, Meltzer, A, Nocquet, JM, Regnier, M, Rolandone, F, Ruiz, M & Soto-Cordero, L 2019, '1D-velocity structure and seismotectonics of the Ecuadorian margin inferred from the 2016 Mw7.8 Pedernales aftershock sequence', Tectonophysics, vol. 767, 228165. https://doi.org/10.1016/j.tecto.2019.228165
León-Ríos, Sergio ; Agurto-Detzel, Hans ; Rietbrock, Andreas ; Alvarado, Alexandra ; Beck, Susan ; Charvis, Phillipe ; Edwards, Benjamin ; Font, Yvonne ; Garth, Tom ; Hoskins, Mariah ; Lynner, Colton ; Meltzer, Anne ; Nocquet, Jean Matthieu ; Regnier, Marc ; Rolandone, Frederique ; Ruiz, M. ; Soto-Cordero, Lillian. / 1D-velocity structure and seismotectonics of the Ecuadorian margin inferred from the 2016 Mw7.8 Pedernales aftershock sequence. In: Tectonophysics. 2019 ; Vol. 767.
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abstract = "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.",
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AU - Rietbrock, Andreas

AU - Alvarado, Alexandra

AU - Beck, Susan

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.

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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.

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KW - Subduction zone

KW - Velocity model

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