A New Seismic Hazard Model for Ecuador

Beauval, Céline; Mariniere, J.; Yépes, Hugo; Audin, Laurence; Nocquet, Jean‐Mathieu; Alvarado, Alexandra; Baize, Stéphane; Aguilar, Jorge; Singaucho, Juan Carlos; Jomard, Hervé

doi:10.1785/0120170259

Cited by 41 publications

(29 citation statements)

References 58 publications

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“…In terms of seismic hazards for the Quito area, our results help to refine previous estimates of earthquake time recurrence (Beauval et al 2014(Beauval et al , 2018. Our estimates for the rate of moment deficit accumulation derived from a 3-D spatially variable interseismic coupling translate into recurrence time for magnitude 6.5 + earthquake to be between 200 and 1100 yr, a value consistent or slightly lower than proposed in previous studies (Beauval et al 2014(Beauval et al , 2018Parra et al 2016).…”

Section: Discussionsupporting

confidence: 86%

Geodetic evidence for shallow creep along the Quito fault, Ecuador

Mariniere

Nocquet

Beauval

et al. 2019

Geophysical Journal International

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SUMMARY Quito, the capital city of Ecuador hosting ∼2 million inhabitants, lies on the hanging wall of a ∼60-km-long reverse fault offsetting the Inter-Andean Valley in the northern Andes. Such an active fault poses a significant risk, enhanced by the high density of population and overall poor building construction quality. Here, we constrain the present-day strain accumulation associated with the Quito fault with new Global Positioning System (GPS) data and Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) analysis. Far field GPS data indicate 3–5 mm yr–1 of horizontal shortening accommodated across the fault system. In the central segment of the fault, both GPS and PS-InSAR results highlight a sharp velocity gradient, which attests for creep taking place along the shallowest portion of the fault. Smoother velocity gradients observed along the other segments indicate that the amount of shallow creep decreases north and south of the central segment. 2-D elastic models using GPS horizontal velocity indicate very shallow (<1 km) locking depth for the central segment, increasing to a few kilometres south and north of it. Including InSAR results in the inversion requires locking to vary both along dip and along strike. 3-D spatially variable locking models show that shallow creep occurs along the central 20-km-long segment. North and south of the central segment, the interseismic coupling is less resolved, and data still allows significant slip deficit to accumulate. Using the interseismic moment deficit buildup resulting from our inversions and the seismicity rate, we estimate recurrence time for magnitude 6.5 + earthquake to be between 200 and 1200 yr. Finally, PS-InSAR time-series identify a 2 cm transient deformation that occurred on a secondary thrust, east of the main Quito fault between 1995 and 1997.

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Section: Discussionsupporting

confidence: 86%

Geodetic evidence for shallow creep along the Quito fault, Ecuador

Mariniere

Nocquet

Beauval

et al. 2019

Geophysical Journal International

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“…Four ground-motion models potentially adapted to the French context are included, based on four different strong-motion databases. The variability of hazard estimates related to the uncertainties on the source model is now compared to the variability related to the uncertainties on the ground-motion model (following Beauval et al 2018). As the source model logic tree includes only one earthquake catalog (i.e., FCAT), the earthquake catalog choice is not included in the uncertainty exploration, and the variability on the hazard estimate must be considered as a lower bound.…”

Section: Source-model Uncertainties Versus Ground-motion Model Uncertmentioning

confidence: 99%

The influence of source- and ground-motion model choices on probabilistic seismic hazard levels at 6 sites in France

Beauval

Bard

Danciu

2020

Bull Earthquake Eng

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“…Peak ground acceleration up to 1.4 g was recorded in Pedernales, 0.52 g in Manta, 0.38 g in Portoviejo, 0.23 g in Chone, and 0.19 g in the Esmeraldas (IGEPN, see Data and Resources). The sequence included more than 3500 aftershocks, the most severe ones occurred on May 18, 2016 with Mw 6.7 to 6.9 [22,51] This sector of the subduction zone, including the entire province of Manabí, has a short seismic record covering the last 120 years that suggests a recurrence interval of approximately 20 years for Mw >7.0 events, and between 70 and 80 years for Mw >7.5 [22,52]. Such subduction-related earthquakes have a recurrence relatively short in comparison with the subduction zones north and south of it [22].…”

Section: Seismotectonic Setting and The 2016 Pedernales Earthquake Sementioning

confidence: 99%

mentioning

confidence: 99%

Landslides Triggered by the 2016 Mw 7.8 Pedernales, Ecuador Earthquake: Correlations with ESI-07 Intensity, Lithology, Slope and PGA-h

et al. 2019

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We provide a dataset of the landslides induced by the 2016 Pedernales megathrust earthquake, Ecuador (Mw 7.8, focal depth of 20 km) and compare their spatial distribution with mapped bedrock lithology, horizontal peak ground acceleration (PGA-h) and the macroseismic intensity based on earthquake-induced environmental effects (ESI-07). We studied 192 coseismic landslides (classified as coherent, disrupted and lateral spreads) located in the epicentral area, defined by the VII to IXESI-07 isoseismals. Based on our findings, lahar deposits, tuffs and volcanoclastic units are the most susceptible to landslides occurrence. Alluvial plains with fluvial loose fine sand are the most susceptible setting for lateral spreading, with a maximum intensity of IXESI-07. The coherent landslides are frequently found in altered shale and siltstone geological units with moderate slopes (8°–16°), with typical intensity ranging between VII and VIIIESI-07. Our analysis draws a typical framework for slope movements triggered by subduction earthquakes in Ecuador. The most dangerous setting is the coastal region, a relatively highly urbanized area located near the epicenter and where liquefaction can trigger massive lateral spreading events. Coherent and disrupted landslides, dominating the more internal hilly region, can be triggered also in moderate slope settings (i.e., less than 10°). Indeed, the regression analysis between seismic intensity, PGA-h and landslide occurrence shows that most of the events occurred at PGA-h values between 0.4 g and 1.2 g, at a distance of 30 to 50 km from the rupture plane. Our database suggests that lithology and hillslope geometry are the main geological/geomorphological factors controlling coseismic landslides occurrence; while the distance from the rupture plane plays a significant role on determining the landslide size. Finally, we underline that coseismically-triggered landslides are among the most common environmental effects occurring during large subduction events that can be effectively used to properly evaluate the earthquake macroseismic field. The landslide inventory we compiled is suitable for assessing the vulnerability of physical environment from subduction earthquakes in Ecuador, and offers a primary data source for future worldwide analysis.

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A New Seismic Hazard Model for Ecuador

Cited by 41 publications

References 58 publications

Geodetic evidence for shallow creep along the Quito fault, Ecuador

Geodetic evidence for shallow creep along the Quito fault, Ecuador

The influence of source- and ground-motion model choices on probabilistic seismic hazard levels at 6 sites in France

Landslides Triggered by the 2016 Mw 7.8 Pedernales, Ecuador Earthquake: Correlations with ESI-07 Intensity, Lithology, Slope and PGA-h

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