Triggered crustal earthquake swarm across subduction segment boundary after the 2016 Pedernales, Ecuador megathrust earthquake

Hoskins, Mariah; Meltzer, A.; Font, Yvonne; Agurto‐Detzel, Hans; Vaca, Sandro; Rolandone, F.; Nocquet, J. M.; Soto‐Cordero, L.; Stachnik, J. C.; Beck, S. L.; Lynner, Colton; Ruiz, Mario; Alvarado, Alexandra; Hernández, Stephen; Charvis, Philippe; Régnier, Marc; León-Ríos, Sergio; Rietbrock, Andreas

doi:10.1016/j.epsl.2020.116620

Cited by 22 publications

(23 citation statements)

References 39 publications

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“…Finally, from the relocated data set displayed in vertical and horizontal profiles, we observed a clustered distribution mainly organized along the slab interface, as described by Agurto-Detzel et al (2019), Meltzer et al (2019 but also at shallower depths (<20 km) in the upper crust as discussed by León-Ríos et al (2019) and Hoskins et al (2020). Here, we provide a description of the seismicity distribution observed throughout the 3DVM.…”

Section: Three-dimensional Velocity Modelmentioning

confidence: 54%

“…(2019) and Hoskins et al. (2020). Here, we provide a description of the seismicity distribution observed throughout the 3DVM.…”

Section: Resultsmentioning

confidence: 97%

“…In the upper crust, several small‐ to large‐scale faults might have been activated after the 2016 Pedernales earthquake. The shallow clustered seismicity observed close to the Esmeraldas segment (∼1°N, P1) is related to crustal extension (Agurto‐Detzel et al., 2019; Hoskins et al., 2020) and can be associated with the activation of the Tanigüe fault (Michaud et al., 2015—see F11 in Figure 1b) which may extend down to ∼15 km reaching a low Vp/Vs rounded‐like body (∼1.80) capable to produce this type of confined earthquakes. To the south (∼1°S), we observe clustered vertically aligned seismicity, at ∼10–15 km depth, in the southernmost profile P9.…”

Section: Interpretation and Discussionmentioning

confidence: 99%

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3D Local Earthquake Tomography of the Ecuadorian Margin in the Source Area of the 2016 Mw 7.8 Pedernales Earthquake

et al. 2021

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Based on manually analyzed waveforms recorded by the permanent Ecuadorian network and our large aftershock deployment installed after the Pedernales earthquake, we derive three‐dimensional Vp and Vp/Vs structures and earthquake locations for central coastal Ecuador using local earthquake tomography. Images highlight the features in the subducting and overriding plates down to 35 km depth. Vp anomalies (∼4.5–7.5 km/s) show the roughness of the incoming oceanic crust (OC). Vp/Vs varies from ∼1.75 to ∼1.94, averaging a value of 1.82 consistent with terranes of oceanic nature. We identify a low Vp (∼5.5 km/s) region extending along strike, in the marine forearc. To the North, we relate this low Vp and Vp/Vs (<1.80) region to a subducted seamount that might be part of the Carnegie Ridge (CR). To the South, the low Vp region is associated with high Vp/Vs (>1.85) which we interpret as deeply fractured, probably hydrated OC caused by the CR being subducted. These features play an important role in controlling the seismic behavior of the margin. While subducted seamounts might contribute to the nucleation of intermediate megathrust earthquakes in the northern segment, the CR seems to be the main feature controlling the seismicity in the region by promoting creeping and slow slip events offshore that can be linked to the updip limit of large megathrust earthquakes in the northern segment and the absence of them in the southern region over the instrumental period.

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Section: Three-dimensional Velocity Modelmentioning

confidence: 54%

“…(2019) and Hoskins et al. (2020). Here, we provide a description of the seismicity distribution observed throughout the 3DVM.…”

Section: Resultsmentioning

confidence: 97%

Section: Interpretation and Discussionmentioning

confidence: 99%

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3D Local Earthquake Tomography of the Ecuadorian Margin in the Source Area of the 2016 Mw 7.8 Pedernales Earthquake

et al. 2021

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“…In the upper crust, several small-to large-scale faults might have been activated after the 2016 Pedernales earthquake. The shallow clustered seismicity observed close to the Esmeraldas segment (∼1°N, P1) is related to crustal extension (Agurto-Detzel et al, 2019;Hoskins et al, 2020) and can be associated with the activation of the Tanigüe fault (Michaud et al, 2015-see F11 in Figure 1b) which may extend down to ∼15 km reaching a low Vp/Vs rounded-like body (∼1.80) capable to produce this type of confined earthquakes. To the south (∼1°S), we observe clustered vertically aligned seismicity, at ∼10-15 km depth, in the southernmost profile P9.…”

Section: Structures Controlling the Seismicitymentioning

confidence: 94%

3D local earthquake tomography of the Ecuadorian margin in the source area of the 2016 Mw 7.8 Pedernales earthquake

León-Ríos

Bie

Agurto‐Detzel

et al. 2020

Preprint

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models were calculated using local earthquake tomography in the region affected by the 2016 Pedernales, Ecuador earthquake • Tomographic images highlight the heterogeneities of the margin affected by seamounts and ridges comprising the oceanic crust • Carnegie Ridge seems the main feature controlling the seismic activity and the offshore extent of large megathrust earthquakes in the region Supporting Information:

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“…These two aftershock ribbons bound laterally the 2016 Mw 7.8 seismic source, supporting the presence of two creeping transition zones there. Many recent studies document very well that aftershock sequence including large aftershocks, seismic swarms, and slow slip events activated by the afterslip on the megathrust interface that occurred during the postseismic period, but also crustal seismic events associated with the reactivation of shallow crustal faults (Agurto-Detzel et al, 2019;Hoskins et al, 2021;Soto-Cordero et al, 2020;Vaca et al, 2018). A wide range of seismic and aseismic slip modes were documented and primarily associated with the seafloor roughness and the subduction of FIGURE 4 | Range of the best GPS-fitting interseismic coupling models with their associated along-trench moment deficit rate.…”

Section: On the Coseismic Sourcementioning

confidence: 97%

Seismic and Aseismic Cycle of the Ecuador–Colombia Subduction Zone

et al. 2021

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The Colombia–Ecuador subduction zone is an exceptional natural laboratory to study the seismic cycle associated with large and great subduction earthquakes. Since the great 1906 Mw = 8.6 Colombia–Ecuador earthquake, four large Mw > 7.5 megathrust earthquakes occurred within the 1906 rupture area, releasing altogether a cumulative seismic moment of ∼35% of the 1906 seismic moment. We take advantage of newly released seismic catalogs and global positioning system (GPS) data at the scale of the Colombia–Ecuador subduction zone to balance the moment deficit that is building up on the megathrust interface during the interseismic period with the seismic and aseismic moments released by transient slip episodes. Assuming a steady-state interseismic loading, we found that the seismic moment released by the 2016 Mw = 7.8 Pedernales earthquake is about half of the moment deficit buildup since 1942, suggesting that the Pedernales segment was mature to host that seismic event and its postseismic afterslip. In the aftermath of the 2016 event, the asperities that broke in 1958 and 1979 both appears to be mature to host a large Mw > 7.5 earthquakes if they break in two individual seismic events, or an Mw∼7.8–8.0 earthquake if they break simultaneously. The analysis of our interseismic-coupling map suggests that the great 1906 Colombia–Ecuador earthquake could have ruptured a segment of 400 km-long bounded by two 80 km wide creeping segments that coincide with the entrance into the subduction of the Carnegie ridge in Ecuador and the Yaquina Graben in Colombia. These creeping segments share similar frictional properties and may both behave as strong seismic barriers able to stop ruptures associated with great events like in 1906. Smaller creeping segments are imaged within the 1906 rupture area and are located at the extremities of the large 1942, 1958, 1979, and 2016 seismic ruptures. Finally, assuming that the frequency–magnitude distribution of megathrust seismicity follows the Gutenberg–Richter law and considering that 50% of the transient slip on the megathrust is aseismic, we found that the maximum magnitude subduction earthquake that can affect this subduction zone has a moment magnitude equivalent to Mw ∼8.8 with a recurrence time of 1,400 years. No similar magnitude event has yet been observed in that region.

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Triggered crustal earthquake swarm across subduction segment boundary after the 2016 Pedernales, Ecuador megathrust earthquake

Cited by 22 publications

References 39 publications

3D Local Earthquake Tomography of the Ecuadorian Margin in the Source Area of the 2016 Mw 7.8 Pedernales Earthquake

3D Local Earthquake Tomography of the Ecuadorian Margin in the Source Area of the 2016 Mw 7.8 Pedernales Earthquake

3D local earthquake tomography of the Ecuadorian margin in the source area of the 2016 Mw 7.8 Pedernales earthquake

Seismic and Aseismic Cycle of the Ecuador–Colombia Subduction Zone

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