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![Comparison of the slip distribution of the 1906 earthquake with the main shocks and aftershocks of the 1958, 1979, and 2016 earthquakes. The slip areas of the 1906 earthquake are displayed by colored squares with slip magnitudes indicated by the color scale. Red contours represent the slip distribution of the 2016 earthquake. Source mechanisms colored red indicate those of the 2016 earthquake (M w 7.7) and its aftershocks. The pink source mechanism is the Global CMT solution of the 1979 earthquake (M w 8.1), and pink stars indicate the epicenters of the 1979 aftershocks. The source mechanism of the 1958 earthquake (M w 7.7) (green) is assumed to be the same as that of the 1979 earthquake, and green stars indicate the epicenters of the 1958 aftershocks. The epicenters of the 1979 and 1958 earthquakes are those estimated by Mendoza and Dewey [1984] with quality A or B. The black rectangle encloses the high interplate coupling patch (C5) corresponding to the source of the 1958 earthquake.](profile/Patricia-Pedraza/publication/314070101/figure/fig2/AS:796681771708416@1566955144336/Comparison-of-the-slip-distribution-of-the-1906-earthquake-with-the-main-shocks-and.png)
Comparison of the slip distribution of the 1906 earthquake with the main shocks and aftershocks of the 1958, 1979, and 2016 earthquakes. The slip areas of the 1906 earthquake are displayed by colored squares with slip magnitudes indicated by the color scale. Red contours represent the slip distribution of the 2016 earthquake. Source mechanisms colored red indicate those of the 2016 earthquake (M w 7.7) and its aftershocks. The pink source mechanism is the Global CMT solution of the 1979 earthquake (M w 8.1), and pink stars indicate the epicenters of the 1979 aftershocks. The source mechanism of the 1958 earthquake (M w 7.7) (green) is assumed to be the same as that of the 1979 earthquake, and green stars indicate the epicenters of the 1958 aftershocks. The epicenters of the 1979 and 1958 earthquakes are those estimated by Mendoza and Dewey [1984] with quality A or B. The black rectangle encloses the high interplate coupling patch (C5) corresponding to the source of the 1958 earthquake.
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A large earthquake (Mw 7.7) occurred on 16 April 2016 within the source region of the 1906 earthquake in the Ecuador-Colombia subduction zone. The 1906 event has been interpreted as a megathrust earthquake (Mw 8.8) that ruptured the source regions of smaller earthquakes in 1942, 1958, and 1979 in this subduction. Our seismic analysis indicated that...
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... of strong interplate coupling occur as isolated patches, designated C1 through C6, along the Ecuadorian coast ( Figure 1c). The slip area of the 2016 earthquake overlaps C3 (Figure 4), indicating that the 2016 event ruptured this asperity. The aftershocks were distributed in and around patches C1, C2, and C4 ( Figure 4). ...
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... slip area of the 2016 earthquake overlaps C3 (Figure 4), indicating that the 2016 event ruptured this asperity. The aftershocks were distributed in and around patches C1, C2, and C4 ( Figure 4). ...
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... time period is roughly half of the time interval between the 1942 and 2016 events. Our tsunami inversion results indicated that the main slip of the 1906 earthquake occurred near the trench offshore of the 1942, 1958, and 1979 source regions (Figure 4), which is different from the source model proposed by Kanamori and McNally [1982]. Since our tsunami inversion resolution in the intermediate and deep subfaults was limited ( Figure S5), we may not be able to rule out the possibility of slip in these regions. ...
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... together, these findings suggest that this hypothesis may generally hold in subduction zones over a wide range of seismic magnitudes, and they imply that the distribution of coupling strength can be used to assess future slip. We consider this possibility here by focusing on the source region of the 1958 earthquake (Figure 4). The slip deficit that has accumulated in C5 since 1958 corresponds to a moment magnitude of 7.6. ...
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... Poco después, este pico de ampli昀椀cación fue con昀椀rmado por Laurendeau et al. (2017), quienes concluyeron que la respuesta sísmica varía entre la parte norte y sur de la ciudad. Esta diferencia, en el grado de ampli昀椀cación de ondas sísmicas entre la parte norte y sur, fue reportada también por Courboulex et al. (2022), quienes, sobre la base de simulaciones numéricas, con昀椀rmaron que un sismo generado en la zona de subducción del Pací昀椀co de magnitud 8,4 -8,8 , similar al de 1906 (Yoshimoto et al. 2017), generaría una ampli昀椀cación en las amplitudes de las ondas sísmicas en frecuencias de alrededor de 0,3Hz en la zona sur de Quito. ...
Las iniciativas de investigación, planificación y gestión de riesgos en Quito se sustentan en esfuerzos colectivos de larga trayectoria. En este libro se ofrece un balance articulado en tres secciones. En la primera se documentan las principales nociones del riesgo: vulnerabilidad y amenaza. El enfoque de la segunda está en la gestión del riesgo, los instrumentos y la información disponibles, pero también las distintas visiones para comprenderlo e interpretarlo. En la tercera se exploran casos emblemáticos, con énfasis en los desafíos del proceso urbano de Quito.Mediante este ejercicio reflexivo, se pone en evidencia la brecha persistente entre la producción de conocimiento y las acciones para reducir la vulnerabilidad y encarar las amenazas. Se trata de una oportunidad para pensar nuevas estrategias de investigación, mejor vinculadas con las posibilidades y limitaciones de la gestión del riesgo en la ciudad.
... Furthermore, this database extends and enhances efforts historically made determining focal mechanisms in the region at both the national and local levels by other researchers such as Molnar and Sykes, 1969;Kafka and Weidner, 1981;Pennington, 1981;Audemard et al, 2005;Cortés and Angelier, 2005;Palma et al., 2010;Dicelis et al., 2016;Gómez-Alba et al., 2016;Poli et al., 2016;Posada et al., 2017;Yoshimoto et al., 2017;Monsalve-Jaramillo et al., 2018;Chang et al., 2019;Londoño et al. 2019;Poveda et al., 2022;Quintanar et al., 2022;Tary et al., 2022;Bishop et al., 2023. Although there are international SMT catalogs with events information in Colombia, like Global Centroid Moment Tensor Catalog (Dziewonski, et al., 1981 andEkström, et al., 2012), the German GEOFON project (Hanka and Kind, 1994;Saul et al., 2011;GFZ, 2023), from the German Research Centre for Geosciences (GFZ) and the United States Geological Survey (https://www.usgs.gov/programs/earthquake-hazards), ...
El Servicio Geológico Colombiano presenta los tensores de momento sísmico y mecanismos focales calculados para sismos localizados en el territorio nacional y regiones fronterizas desde 2014 hasta 2021. Estas soluciones se obtuvieron usando diferentes métodos basados en inversión de formas de onda (SWIFT, SCMTV, Fase W e ISOLA) y polaridades de primeros arribos (FPFIT). Esta información se ha organizado en una base de datos y se ha dispuesto al público mediante una página web por medio de la cual se pueden hacer búsquedas por fechas, área circular o cuadrante. Las soluciones del centroide del tensor de momento son fundamentales para comprender la geometría de la falla, la fuente sísmica que produce un sismo, su magnitud, y la energía liberada por el mismo. Igualmente, gracias a esta información es posible hacer interpretaciones sobre la tectónica de placas, análisis de esfuerzos de la corteza terrestre y su dinámica, modelos dinámicos y cinemáticos de la fuente, análisis de fallas activas y potencial tsunamigénico de sismos, entre otros aspectos.
... It was the fifth event above magnitude 7.5 that occurred in the region since 1900. The first and largest was the Mw 8.4-8.8 1906 event (Kanamori & McNally, 1982;Yoshimoto et al., 2017), which ruptured a 200-500 km-long portion of the Ecuador-Colombia subduction zone (Kelleher, 1972). Three other Mw 7.7-8.2 ...
... The Pedernales earthquake broke the highly coupled southern segment, similar to the 1942 earthquake Nocquet et al., 2014Nocquet et al., , 2017. It may have released all of the strain stored since 1942 (Ye et al., 2016;Yoshimoto et al., 2017), or may have released more strain than what was accumulated since 1942, thus hinting at the existence of an earthquake supercycle and explaining the apparent quiescence of the Ecuador-Colombia subduction zone before 1906 (Nocquet et al., 2017). 10.1029/2022JB025353 3 of 19 streaks going from the rupture zone to the trench, which are permanent features of the background seismicity (Font et al., 2013). ...
Subduction zones are highly heterogeneous regions capable of hosting large earthquakes. To better constrain the processes at depth, we analyze the source properties of 1514 aftershocks of the 16th April 2016 Mw 7.8 Pedernales earthquake (Ecuador) using spectral ratios. We are able to retrieve accurate seismic moments, stress drops, and P and S corner frequencies for 341 aftershocks, including 136 events belonging to families of repeating earthquakes. We find that, for the studied magnitude range (Mw 2–4), stress drops appear to increase as a function of seismic moment. They are also found to depend on their distance to the trench. This is in part explained by the increase in depth, and therefore normal stress, away from the trench. However, even accounting for the shallow depths of earthquakes, stress drops appear to be anomalously low near the trench, which can be explained by a high pore fluid pressure or by inherent properties of the medium (low coefficient of friction/low rigidity of the medium) in that region. We are also able to examine the temporal evolution of source properties thanks to the presence of repeating earthquakes. We find that the variations of source properties within repeating earthquake families are not uniform, and are highly spatially variable over most of the study area. This is not the case near the trench, however, where stress drops systematically decrease over time. We suggest that this reflects an increase in pore fluid pressure near the trench over the postseismic period.
... ) and 2016 (Mw 7.8), sometimes accompanied by tsunamis (See Fig. 1 for location). Therefore, this region has been deeply studied by many authors (e.g., Mothes et al., 2013;Nocquet et al., 2014;Chlieh et al., 2014;Ye et al., 2016;Yoshimoto et al., 2017;Yamanaka et al., 2017;Mora-Páez et al., 2019;Sagiya and Mora-Páez., 2020). ...
... All the GPS sites, except VORI and CN42, have more than 2.0 years of data. The shorter period of VORI is associated with the omission of the data affected by coseismic and post-seismic signals of the M w 7.8 earthquake that struck the coast of Ecuador on April 16th, 2016 (Yoshimoto et al., 2017). The station CN42, on the other hand, has corrupted data files (in "Receiver Independent Exchange" = RINEX format) during the latest period of 2016 and throughout 2017. ...
... There is the conjunction of the Pacific, Cocos and Nazca oceanic plates as well as the Galapagos microplate besides their interaction with the Caribbean and South American continental plates ( Fig.1) (Lonsdale, 1988;Klein et al., 2005;Pennington, 1981;Gailler et al., 2007). Out of this constellation result seismic movements with the generation of strong earthquakes and severe tsunamis as recorded in past history (Mendoza & Dewey, 1984;Sennson & Beck, 1996;Graindorge et al., 2004;Pararas-Carayannis & Zoll, 2017;Yamanaka et al., 2017;Pulido et al., 2020;Yoshimoto et al., 2017). There are several studies about Ecuador´s past tsunami impacts and associated seismic hazards, paleo-tsunami deposits, economic damages, prevention and mitigation efforts as well as the vulnerabilities of the public and the infrastructure (Chunga and Toulkeridis, 2014;Toulkeridis, 2016;Matheus Medina et al., 2016;Rodríguez Espinosa et al., 2017;Chunga et al., 2017;Toulkeridis et al., 2018;Mato and Toulkeridis, 2018;Navas et al., 2018;Celorio-Saltos et al., 2018;Matheus-Medina et al., 2018;Chunga et al., 2019;Martinez and Toulkeridis, 2020;Edler et al., 2020;Suárez-Acosta et al., 2021;Del-Pino-de-la-Cruz et al., 2021;Aviles-Campoverde et al., 2021). ...
There are a number of unusual tsunamis, which occur within the continents rather than in the oceans, named inland tsunamis. One of these rare occasions occurred in the morning of the Friday the 13th October 2000 in a volcanic glacial lake of the horseshoe shaped extinct El Altar volcano in central Ecuador. A detailed mapping of available air photos and satellite images have been reviewed and evaluated in order to reconstruct the catastrophic event of 2000 and a previous one, evidencing that climate change and the associated subsequent reduction of the glacial caps have been responsible for the disassociation of a huge mass of rock(s), of which separation has resulted to an impact in the volcanic lake by an almost free fall of some 770 meters above lake level ground. This impact generated a tsunami wave capable to reach an altitude of 125 meters about the lake ́s water level and leave to lower grounds killing some ten people and hundreds of animals with a mixture of a secondary lahar and debris avalanche. We tried to explain how the fall has occurred with some theoretical considerations, which resulted to imply that the rock hit at least once, probably twice the caldera wall prior lake impact. Such phenomena, even if rare, need to be better monitored in order to avoid settlements in potential areas in the reach of such devastating waves and subsequent avalanches, even more so, when due to climate change the accumulation of water in such lakes increases and the corresponding subglacial erosion and corresponding disassociation of lose rock material may set free more rocks with substantial volumes.
... Figure modified from Alvarado et al. (2014). (Yoshimoto et al. 2017). The last large earthquake occurred on 2016 April 16 (Pedernales earthquake, M w 7.8). ...
In 1906, an earthquake with a magnitude estimated between Mw 8.4 and 8.8 occurred in the subduction zone along the coast of Ecuador and Colombia. This earthquake caused extensive damage on the coast but had a rather small impact on the capital city of Quito, situated 180 km away. At that time, the city of Quito extended over a small area with a few thousand inhabitants, while today it stretches over 40 km and has a population of over 3 million, with most of the city built without paraseismic regulations. The aim of this study is to obtain new insights on the impact that large earthquakes from the subduction zone would have on the city today. This question is crucial since we know that the city of Quito is prone to site effects and that the southern part of the city amplifies seismic waves at low frequencies, around 0.3-0.4 Hz (Laurendeau et al., 2017). In April 2016, an Mw 7.8 earthquake occurred on the subduction interface in the Pedernales area. This event was the first large earthquake in the city of Quito to be well recorded by 13 stations of the permanent accelerometric network (RENAC). In this study, we take advantage of this dataset (mainshock and large aftershock recordings) to (1) test an empirical Green's function blind simulation approach where the input stress drop is taken from a global catalog of source time functions, (2) compare the synthetic accelerograms and ground motion values we obtain for an Mw 7.8 earthquake with the actual recordings of the Pedernales earthquake, and then (3) simulate larger earthquakes of Mw 8.2 and Mw 8.5 from the subduction zone. For Mw 7.8 simulations, our approach allows a good reproduction of the ground motions in the whole frequency bands and properly takes into account site effects. For Mw 8.2 and Mw 8.5 simulations, we obtain for the stations in the southern part of the basin, larger values at low frequencies than the predicted motion given by Ground Motion Models (GMMs). These values, although high, should be supported by new or recent buildings if they are constructed respecting the building code that applies in Quito. Therefore, for this type of strong but distant earthquake, the seismic standards appear to be well suited and it is imperative to ensure that they are well considered in the design of the new buildings to be constructed, especially in the southern part of the expanding city.
... Nearly 4.2 million people live within 10 km from the coast [43]; whereby a significant fraction is concentrated in few cities, e.g., Esmeraldas city, Bahí a de Cará quez, Manta, La Libertad, Salinas, and Playas (i.e., combined projected population of 675,670 inhabitants at 2020) [43]. Among these, Esmeraldas city (northern coast) is of particular interest considering its population (i.e., among the ten most densely populated cities and highly touristic), strategic industrial activities (port, fishery, and oil refinery), and geographic location of high seismicity [10,19,20,44,45]. ...
... Among the significant EQ recorded in the study area are: the 1906 strongest event of Mw 8.8, which has been recently proposed as Mw 8.4 [45] with a rupture area of approx. 500 Km as found by Kelleher (1972) at [18,67], the 1942 EQ Mw 7.8 which had a probable rupture extension of 80 km Beck and Ruff, 1989 [12], the 1958 EQ Mw 7.7 which ruptured a length of 110 km [12,18], the 1979 EQ Mw 8.2 ruptured approx. ...
... 500 Km as found by Kelleher (1972) at [18,67], the 1942 EQ Mw 7.8 which had a probable rupture extension of 80 km Beck and Ruff, 1989 [12], the 1958 EQ Mw 7.7 which ruptured a length of 110 km [12,18], the 1979 EQ Mw 8.2 ruptured approx. 230 km [18], the 1998 EQ Mw 7.2 in front of Bahia de Caraquez [12,69], and the 2016 EQ Mw 7.8 which rupture length was 100-120 km [13,70] and according to several authors, overlaps the 1942 EQ segment [13,45,70,71]. Toward the south, strong activities have been also recorded with events of magnitudes between 6.9-7.5 around the Gulf of Guayaquil [12] and further along Perú coast [67]. ...
The current study investigated the probable impact from a tsunami to a populated area located along the northwest ecuadorian coast, specifically in the key oil-industrial city of esmeraldas. a numerical tsunami simulation was performed considering the seismological and tectonic aspects of the area. The damage probability was calculated using fragility functions (ffs). Briefly, 16 cases of source models with slightly different fault parameters were tested, where one was selected as the worst scenario of tsunami inundation. This scenario was a hypothetic earthquake case (mw 8.7) located in front of esmeraldas city, approximately 100 km offshore along the ecuador—colombia trench, with three shallow fault segments (top depth of 10 km), a strike aligned with the trench axis, a middle dip angle of 28°, assuming large slips of 5 to 15 m, and a rake angle of 90°. The results from the numerical simulation were comparable to a similar study previously conducted and with those of historically documented data. The tsunami damage estimation using FFs resulted in estimated damages of 50% and 44% in exposed buildings and population, respectively. Results also showed that the most impacted areas were located next to the coastal shoreline and river. tourism, oil exports, and port activities, in general, would be affected in this scenario; thus, compromising important industries that support the national budget. Results from this study would assist in designing or improving tsunami risk reduction strategies, disaster management, use of coastal zones, and planning better policies.
... Although seismic hazard in Bogota is essentially controlled by nearby crustal faults, the city has also experienced strong ground shaking from megathrust subduction earthquakes in the Pacific coast of Colombia in 1906 (Mw8.5) [5,6,7] and 1979 (Mw8.1) [8]. ...
Bogotá, a megacity with almost 8 million inhabitants is prone to a significant earthquake hazard due to nearby active faults as well as subduction megathrust earthquakes. The city has been severely affected by many historical earthquakes in the last 500 years, reaching MM intensities of 8 or more in Bogotá. The city is located at a large lacustrine basin extending approximately 40 km from North to South and East to West. The sediment infill of the basin is composed of very thick and soft clay deposits (up to 300 m in thickness) in wide areas of the basin, as well as alluvial deposits from rivers towards the South of the basin. We constructed the first 3D velocity model of the basin based on dense microtremors arrays measurements (radius from 60 cm to 1700 m) at 300 sites within the basin as well as single microtremors measurements at 800 points, which allowed us to estimate in detail the velocity model of the basin from the shallow deposits up to the seismic bedrock. Our dense single microtremors measurements in Bogota indicate that horizontal to vertical ratios of microtremors are characterized by large predominant peaks for periods as large as 4 seconds, near the center of the basin. To constraint the geometry of the basin we used available gravity data at approximately 400 points, as well as available geological information from boreholes within the basin. Our results show that the deepest point of the Neogene-Quaternary deposits reach a depth of 800 m with a bottom S wave velocity of 700 m/s. The seismic bedrock (Cretaceous sandstones, Vs=3000 m/s) reach a depth of 3800 m at the deepest point of the basin. We simulated three-dimensional long period ground motions at Bogota from a shallow crustal earthquake near the basin (2008/05/24, Mw5.9, depth 10km), using a discontinuous grid finite difference method. Our results show the generation of large amplitude and long duration surface waves at the basin in agreement with records of this earthquake at the strong motion network of Bogota.
... This subduction segment has experienced the great (Mw > 8.5) 1906 Colombia-Ecuador megathrust earthquake; however, many uncertainties remain on its exact moment magnitude that fluctuates from 8.5 to 9.0 in the scientific literature and on its rupture length that is proposed between 300 and 500 km long (Kanamori and McNally, 1982;Kelleher, 1972;Mendoza and Dewey, 1984). From the analysis of long-period surface wave records, it was suggested that the 1906 earthquake did not exceed Mw 8.5 (Okal, 1992), a magnitude similar from its associated tsunami's height modeling with a rupture length of ∼300 km (Tsuzuki et al., 2017;Yoshimoto et al., 2017). Reassessments of the 1906 seismic moment suggest a moment magnitude Mw 8.6 (Ye et al., 2016) that will be our reference moment magnitude for this study (Table 1). ...
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.
... Also of note, on April 16, 2016, 2 months before the onset of seismic unrest at Cayambe, the M w 7.8 Pedernales thrust earthquake struck the coast of Ecuador, 200 km from Cayambe (Heidarzadeh et al., 2017;Nocquet et al., 2017;Yoshimoto et al., 2017). This event caused MMI intensity III to IV ground shaking around Cayambe, and was followed by seven M w > 6.0 events in the following 3 months (USGS, 2021). ...
Cayambe Volcano is an ice-capped, 5,790 m high, andesitic-dacitic volcanic complex, located on the equator in the Eastern Cordillera of the Ecuadorian Andes. An eruption at Cayambe would pose considerable hazards to surrounding communities and a nationally significant agricultural industry. Although the only historically documented eruption was in 1785, it remains persistently restless and long-period (LP) seismicity has been consistently observed at the volcano for over 10 years. However, the sparse monitoring network, and complex interactions between the magmatic, hydrothermal, glacial, and tectonic systems, make unrest at Cayambe challenging to interpret. In June 2016 a seismic “crisis” began at Cayambe, as rates of high frequency volcano-tectonic (VT) earthquakes increased to hundreds of events per day, leading to speculation about the possibility of a forthcoming eruption. The crisis began 2 months after the M w 7.8 Pedernales earthquake, which occurred on the coast, 200 km from Cayambe. Here we show that the 2016 seismicity at Cayambe resulted from four distinct source processes. Cross correlation, template matching, and spectral analysis isolate two source regions for VT earthquakes–tectonic events from a regional fault system and more varied VTs from beneath the volcanic cone. The temporal evolution of the LP seismicity, and mean Q value of 9.9, indicate that these events are most likely generated by flow of hydrothermal fluids. These observations are consistent with a model where a new pulse of magma ascent initially stresses regional tectonic faults, and subsequently drives elevated VT seismicity in the edifice. We draw comparisons from models of volcano-tectonic interactions, and speculate that static stress changes from the Pedernales earthquake put Cayambe volcano in an area of dilation, providing a mechanism for magma ascent. Our findings provide a better understanding of “background” seismicity at Cayambe allowing faster characterization of future crises, and a benchmark to measure changes driven by rapid glacial retreat.
