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The Instituto Geofísico of the Escuela Politécnica Nacional (IGEPN) is in charge of the monitoring and study of seismic and volcanic activity in the Ecuadorean territory. This institution currently maintains the Servicio Nacional de Sismología y Vulcanología (The National Seismology and Volcanology Service), which includes monitoring via modern sei...
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... We analyze data from VCH1, a seismic-acoustic station in the permanent network of the Instituto Geofísico, Escuela Politécnica Nacional (Alvarado et al., 2018); the station has a three-component Trillium Compact 120 , and the approximate location of the pre-eruptive seismic tremor (region bounded by the green dashed line after Li et al., 2022). We highlight the two large magnitude five earthquakes (red circles) as well as earthquakes of magnitude 4 (purple circles) occurring 2 hours before the reported eruption onset (Stage II). ...
The 2018 eruption of Sierra Negra volcano, Galápagos, Ecuador has provided new insights into the mechanisms of caldera resurgence, subsidence, and fissuring at basaltic shield volcanoes. Here, we integrate local (∼0.4 km) seismo‐acoustic records and regional (∼85 km) infrasound array data to present new observations of the 2018 Sierra Negra eruption with improved time and spatial resolutions. These observations include: air‐to‐ground coupling ∼2 hr before the time of the eruption onset, migration of the infrasound tremor from 22:54 June 26 to 12:31 June 27 UT (all times in UT), and persistent infrasound detections during the weeks between 5 July and 18 August from an area that does not coincide with the previously documented eruptive fissures. We interpret air‐to‐ground coupling as infrasound tremor generated in the nearby fissures before the main eruptive phase started, although ambiguity remains in interpreting a single seismic‐infrasonic sensor pair. The progressive location change of the infrasound tremor agrees with the migration of the eruption down the north flank of Sierra Negra at a rate of ∼0.15 ± 0.04 m/s. The weeks‐long persistent detections coincide with a region that has thermal anomalies, co‐eruptive deformation, lava fields, and geological features that could be interpreted as multiple lava tube skylights. Our observations and interpretations provide constraints on the mechanisms underlying fissure formation and magma emplacement at Sierra Negra.
... Para los sismos de magnitud menor a M = 4.5 y mayor a M = 3.5 el periodo de completitud comienza en 1997 (Beauval et al., 2013). La completitud para las magnitudes hasta M = 3.0 se alcanzó en el 2008 (Alvarado et al., 2018). ...
... Desde la instalación del sistema SeisComP3 el IG reporta magnitudes de momento sísmico (Alvarado et al., 2018). Los eventos previos a la instalación de este sistema han sido homogenizados para tener todo el catálogo en magnitud de momento (Beauval et al., 2013). ...
El 16 de abril de 2016 ocurrió un terremoto en Ecuador de magnitud 7.8 el cual causó enormes pérdidas humanas y materiales, y miles de personas heridas y desplazadas. Este evento sísmico forma parte de un conjunto de sismos en la provincia de Manabí en la región costera de Ecuador donde se produce la subducción de la placa de Nazca bajo la placa Sudamericana. Proponemos estudiar este conjunto de sismos desde la perspectiva de la mecánica estadística no extensiva utilizando el concepto de entropía propuesta por Tsallis en (Tsallis, 2009). Desarrollamos el cálculo del coeficiente de complejidad q para la magnitud de los sismos, parámetro que cuantifica el valor de complejidad de un sistema, y lo aplicamos al catálogo de terremotos en la zona de alto acoplamiento sísmico de Manabí-Esmeraldas en la zona de subducción de Ecuador. Los resultados muestran una relación entre los cambios en el coeficiente de complejidad q a través del tiempo y la ocurrencia de sismos de gran magnitud M>5. El terremoto del 16 de abril de 2016 acompaña un previo incremento en el valor de q el cual coincide con otros estudios anteriores como en (Papadakis et al., 2015).
... Ecuador, also involved in the CASA project with ∼90 campaign-style GPS sites, established the National Geodetic Network (RENGEO) in 2006, initially focused on areas with greater volcanic activity. In 2008, it was expanded into a regional network today composed of 80 continuous GNSS stations countrywide with a focus on the tectonically active regions (Alvarado et al., 2018). The RENGEO network is mostly composed of Trimble receivers: Trimble NetRS, NetR9, and Alloy; with three stations operating a Leica GR50. ...
Colombia and Ecuador sit at one of the most diverse tectonic regimes in the world, located at the intersection of five tectonic plates (Bird, 2003) encompassing many geophysical hazard regimes, multiple subduction zones, and broad diffuse areas of significant deformation. Notably, the subduction of the Nazca plate under South America has produced at least seven large (>Mw 7) and damaging earthquakes since 1900—the largest being the 1906 Mw 8.8 event. Both Colombia and Ecuador have made significant investments in Global Navigation Satellite System (GNSS) networks to study tectonic and volcanic deformation. Earthquake early warning (EEW) systems like the U.S.-operated ShakeAlert system (Murray et al., 2018, 2023) utilize real-time Global Navigation Satellite System (RT-GNSS) to rapidly characterize the largest, most damaging earthquakes in situations where seismic networks alone saturate (Melgar et al., 2015, 2016; Allen and Melgar, 2019; Ruhl et al., 2019). Both Colombia and Ecuador have large vulnerable populations proximal to the coast that may sustain significant damage in these large subduction events (Pulido et al., 2020) and yet farther enough away that an RT-GNSS EEW system could offer significant warning times to these populations and associated infrastructure. We examine the status of the Servicio Geológico Colombiano Geodesia: Red de Estudios de Deformación GNSS network in Colombia and the Escuela Politécnica Nacional GNSS network in Ecuador, their spatial distribution, and the current status of their data streams to determine what augmentations are required to support the real-time detection and modeling of large destructive earthquakes in and near Colombia and Ecuador.
... Low interseismic coupling and creeping on the subduction interface contrast with strong interseismic coupling regions to the north characterized by large earthquake occurrence Nocquet et al., 2014;Villegas-Lanza et al., 2016). Crustal faults in the onshore and offshore region of the Gulf of Guayaquil basin are seismically active (e.g., Puná fault zone), as revealed by strong to moderate present-day seismicity (Alvarado et al., 2018;Vaca et al., 2019) and morpho-tectonics analysis (Dumont et al., 2005). ...
... Few historical subduction earthquakes with intermediate magnitudes are located in the region (e.g., Beauval et al., 2013). However crustal faults are seismically active in the onshore and offshore region of the Gulf of Guayaquil basin (e.g., Puná dextral fault zone; Fig. 5), as revealed by national earthquakes catalogue (Alvarado et al., 2018). The gravitational sliding on the basal décollement levels is slow and appears aseismic, due to overpressured shales, sedimentary loading and tectonic strains. ...
... In Ecuador, local seismic networks have densified since 2010 (Font et al., 2011Regnier et al., 2016;Alvarado et al., 2018;Meltzer et al., 2019) on the coastal margin in the hope of sharpening microseismicity resolution. The subsequent large volumes of continuous data obtained from temporary experiments have considerably increased and exploded after the 2016 Pedernales earthquake due to international postseismic deployments (Meltzer and Beck, 2016;Regnier et al., 2016). ...
... The authors used the OSISEC local seismic network that was installed around La Plata Island-a 50 × 50 km region known for the recurrence of seismic swarms and SSE in central Ecuador (Fig. 1a). This network complements the RENSIG national permanent network installed all across the country (Red Nacional de Sismógrafos del Instituto Geofisico; Alvarado et al., 2018). In total, we used 14 broadband (120 s) seismometer stations, including 4 ocean-bottom seismometers (OBSs). ...
... The magnitude of earthquakes ranges from 1.9 to 4.5. . Red dots, seismicity; orange triangles, broadband stations from the RENSIG permanent network (Alvarado et al., 2018); gray triangles, the OSISEC temporary experiment (seismometers; four OBS also include hydrophones); stations CABP, FLFR, and SEVS were not used by Segovia et al. (2018) to locate the seismicity. In blue is the IRIS-USGS postseismic deployment (Meltzer and Beck, 2016) . ...
Although seismological networks have densified along the Ecuadorian active margin since 2010, visual phase reading, ensuring high arrival times quality, is more and more time-consuming and becomes impossible to handle for the very large amount of recorded seismic traces, even when preprocessed with a detector. In this article, we calibrate a deep-learning-based automatized workflow to acquire accurate phase arrival times and build a reliable microseismicity catalog in the central Ecuadorian forearc. We reprocessed the dataset acquired through the OSISEC local onshore–offshore seismic network that was already used by Segovia et al. (2018) to produce a reference seismic database. We assess the precision of phase pickers EQTransformer and PhaseNet with respect to manual arrivals and evaluate the accuracy of hypocentral solutions located with NonLinLoc. Both the phase pickers read arrival times with a mean error for P waves lower than 0.05 s. They produce 2.7 additional S-labeled picks per event compared to the bulletins of references. Both detect a significant number of waves not related to seismicity. We select the PhaseNet workflow because of its ability to retrieve a higher number of reference picks with greater accuracy. The derived hypocentral solutions are also closer to the manual locations. We develop a procedure to automatically determine thresholds for location attributes to cull a reliable microseismicity catalog. We show that poorly controlled detection combined with effective cleaning of the catalog is a better strategy than highly controlled detection to produce comprehensive microseismicity catalogs. Application of this technique to two seismic networks in Ecuador produces a noise-free image of seismicity and retrieves up to twice as many microearthquakes than reference studies.
... We use data from several regional continuous (cGPS) and episodic GPS data from a collaborative project between the French National Research Institute for Sustainable Development (IRD), the Geophysical Institute (IG-EPN; Mothes et al. 2013 ;Alvarado et al. 2018 ), the Military Geographical Institute of Ecuador (IGM 2021 ) and the Geophysical Institute of Peru (IGP). We integrate data of 21 cGPS sites from the GeoRED Project (Geodesia: Red de Estudios de Deformaci ón) in Colombia, which is run by the Space Geodesy Research Group from the Colombian Geological Surv e y (SGC; Mora-P áez et al. 2018 Dow et al. 2009 ). ...
Northwestern South America is a plate boundary zone where the Nazca, Caribbean and South American plates interact to produce a wide area of active continental deformation from the Gulf of Guayaquil (latitude 3○S) to Venezuela. Previous studies have identified a ∼2000 km long continental sliver, referred as the North Andean Sliver (NAS), squeezed between the Nazca, Caribbean, and South American plates, and escaping at ∼1 cm/yr northeastward with respect to South America. Subduction of the Nazca plate beneath the NAS has produced a sequence of large and great earthquakes during the 20th century along the coast of Ecuador and Colombia. Large crustal earthquakes up to magnitude 7.7 have been documented along the proposed eastern boundary of the NAS. However, active tectonics data, historical and recent earthquakes all indicate active fault systems within the NAS, possibly resulting from the interaction of several tectonic blocks. Here, we derive an extensive horizontal velocity field using continuous and episodic GNSS data from 1994 to 2019.9, covering northern Peru, Ecuador, Colombia, Panama and Venezuela. We model the GNSS velocity field using a kinematic elastic block approach that simultaneously solves for rigid tectonic block rotations and interseismic coupling along the subduction interfaces and along major crustal faults. In contrast to previous results that considered a single rigid NAS, our dense GNSS velocity field demonstrates that the NAS undergoes significant internal deformation and cannot be modeled as single rigid block. We find that block kinematics in the northern Andes are well described by the rotation of 6 tectonic blocks, showing increasing eastward motion from south to north. The Eastern boundary of the sliver is defined by a right-lateral transpressive fault system accommodating 5.6 to 17 mm/yr of motion. Fragmentation of the NAS occurs through several fault systems with slip rates of 2-4 mm/yr. Slow reverse motion is found across the sub-Andean domain in Ecuador and northern Peru at 2-4 mm/yr, marking a transitional area between the NAS and stable South America. In contrast, such a transitional sub-Andean domain does not exist in Colombia and western Venezuela. At the northwestern corner of Colombia, fast (∼15 mm/yr) eastward motion of the Panama block with respect to the NAS results in arc-continent collision. We propose that the Uramita fault and Eastern Panama Deformed Zone define the current Panama/NAS boundary, accommodating 6 and 15 mm/yr of relative motion, respectively. A fraction of the Panama motion appears to transfer northeastward throughout the San Jacinto fold belt and as far east as longitude ∼75○W. Along the Caribbean coast, our model confirms, slow active subduction at ∼4.5 mm/yr along the South Caribbean Deformed Belt offshore northern Colombia and a relatively uniform rate of ∼1-2 mm/yr offshore northern Venezuela. Along the Nazca/NAS subduction interface, interseismic coupling shows a first-order correlations between highly locked patches and large past earthquake ruptures. These patches are separated by narrow zones of low/partial coupling where aseismic transients are observed. Compared to previous studies, our interseismic coupling model highlights the presence of deep coupling down to 70 km in Ecuador.
... Low interseismic coupling and creeping on the subduction interface contrast with strong interseismic coupling regions to the north characterized by large earthquake occurrence Nocquet et al., 2014;Villegas-Lanza et al., 2016). Crustal faults in the onshore and offshore region of the Gulf of Guayaquil basin are seismically active (e.g., Puná fault zone), as revealed by strong to moderate present-day seismicity (Alvarado et al., 2018;Vaca et al., 2019) and morpho-tectonics analysis (Dumont et al., 2005). ...
... Few historical subduction earthquakes with intermediate magnitudes are located in the region (e.g., Beauval et al., 2013). However crustal faults are seismically active in the onshore and offshore region of the Gulf of Guayaquil basin (e.g., Puná dextral fault zone; Fig. 5), as revealed by national earthquakes catalogue (Alvarado et al., 2018). The gravitational sliding on the basal décollement levels is slow and appears aseismic, due to overpressured shales, sedimentary loading and tectonic strains. ...
The offshore Tumbes-Guayaquil forearc basin in the accretionary prism of Northern Peru-Southern Ecuador shows evidence of gravity-driven large-scale deformation systems active during the Late Neogene-Quaternary period. Subsurface data and the construction of eight structural cross-sections show that the ∼8 km-thick Oligocene-Quaternary sedimentary infill is detached seaward and completely decoupled from the underlying inner accretionary prism systems. The Corvina décollement in the Tumbes basin and the Posorja décollement in the Guayaquil basin constitute two thin-skinned gravity tectonic systems associated with kilometer-scale, updip “raft” extensional structures paired with downdip fold-thrust systems (Barracuda and Domito thrust systems). Although many previous studies have described the structural and stratigraphic architecture of the Tumbes-Guayaquil forearc basin, no model explicitly accounts for this anomalous large-scale gravity tectonics. We propose that this gravity tectonic style, more commonly observed in passive continental margins, is primarily controlled by the combination of tectonostratigraphic features, including crustal-scale transtensional deformation related to oblique convergence along the Northern Andean margin, basal décollement slope tilting, strong sediment accumulation, and the presence of overpressured shales.
... We examine 14 months of postseismic data of the Pedernales earthquake, using both the permanent Ecuadorian seismic network (Alvarado et al., 2018), as well as the temporary seismic stations deployed for 1 year after the Pedernales earthquake (Agurto-Detzel et al., 2019;Meltzer et al., 2019). We use the aftershock catalog published by Agurto-Detzel et al. (2019) using both automatic and manual detections and located with a 1D model ( Figure 2). ...
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.
... Seismo-acoustic wave conversion and coupling commonly occur (e.g., Ichihara et al. 2012;Matoza and Fee 2014;; thus, collocated seismic and infrasonic sensor deployments reduce ambiguity in seismicacoustic signal type identification and process discrimination (e.g., Iguchi and Ishihara 1990;Garcés et al. 1998;Ripepe et al. 2001;Lees et al. 2004;Johnson et al. 2005;Matoza et al. 2009aMatoza et al. , b, 2019bIchihara et al. 2021) and in explosive eruption detection and localization (e.g., Matoza et al. , 2017Sanderson et al. 2020;Le Pichon et al. 2021). At present, seismic and infrasound networks have become indispensable components in tracking the geophysical signatures of unrest and eruption, enabling better monitoring and mitigation of volcanic hazards (e.g., Moran et al. 2008a; National Academies of Sciences, Engineering, and Medicine 2017; Alvarado et al. 2018;Power et al. 2020). In the marine environment, technological advances and increasing availability of hydroacoustic systems and ocean-bottom seismology are expanding volcano seismology and acoustics to partially submerged and submarine oceanic volcanoes (e.g., Talandier and Okal 1987;Yamasato et al. 1993;Caplan-Auerbach and Duennebier 2001;Dziak et al. 2005Dziak et al. , 2011Chadwick et al. 2008Chadwick et al. , 2012Green et al. 2013;Metz et al. 2016;Caplan-Auerbach et al. 2017;Metz and Grevemeyer 2018;Tepp et al. 2019Tepp et al. , 2020Talandier et al. 2020;Tepp and Dziak 2021;Rose and Matoza 2021). ...
... The 1980s also saw steady expansion of volcano-seismic monitoring capacities worldwide. For example, in 1988, the Instituto Geofísico of the Escuela Politécnica Nacional (IGEPN) of Ecuador began continuous monitoring of Ecuadorian volcanoes with single telemetered seismic stations at Tungurahua, Cotopaxi, Cuicocha, Chimborazo, Antisana, and Cayambe, and seismic and geodetic networks were established at Guagua Pichincha (Alvarado et al. 2018). Several volcanological and seismological observatories were also established in Colombia by the Colombian Geological Survey (formerly Instituto Colombiano de Geología y Minería INGEOMI-NAS) in the late 1980s (Vargas et al. 2018). ...
... Permanent volcano monitoring networks have progressively established denser seismic networks (Figs. 1 and 5), with continuous digital waveform acquisition, processing, and storage now being the standard. Infrasound technology has been increasingly integrated in volcano-seismic monitoring operations and is also rapidly becoming standard (e.g., Orazi et al. 2013;Ruiz et al. 2013;Iguchi 2016;Coombs et al. 2018;Alvarado et al. 2018;Yokoo et al. 2019;Taisne et al. 2019;Power et al. 2020). ...
Since the 1919 foundation of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI), the fields of volcano seismology and acoustics have seen dramatic advances in instrumentation and techniques, and have undergone paradigm shifts in the understanding of volcanic seismo-acoustic source processes and internal volcanic structure. Some early twentieth-century volcanological studies gave equal emphasis to barograph (infrasound and acoustic-gravity wave) and seismograph observations, but volcano seismology rapidly outpaced volcano acoustics and became the standard geophysical volcano-monitoring tool. Permanent seismic networks were established on volcanoes (for example) in Japan, the Philippines, Russia, and Hawai‘i by the 1950s, and in Alaska by the 1970s. Large eruptions with societal consequences generally catalyzed the implementation of new seismic instrumentation and led to operationalization of research methodologies. Seismic data now form the backbone of most local ground-based volcano monitoring networks worldwide and play a critical role in understanding how volcanoes work. The computer revolution enabled increasingly sophisticated data processing and source modeling, and facilitated the transition to continuous digital waveform recording by about the 1990s. In the 1970s and 1980s, quantitative models emerged for long-period (LP) event and tremor sources in fluid-driven cracks and conduits. Beginning in the 1970s, early models for volcano-tectonic (VT) earthquake swarms invoking crack tip stresses expanded to involve stress transfer into the wall rocks of pressurized dikes. The first deployments of broadband seismic instrumentation and infrasound sensors on volcanoes in the 1990s led to discoveries of new signals and phenomena. Rapid advances in infrasound technology; signal processing, analysis, and inversion; and atmospheric propagation modeling have now established the role of regional (15–250 km) and remote (> 250 km) ground-based acoustic systems in volcano monitoring. Long-term records of volcano-seismic unrest through full eruptive cycles are providing insight into magma transport and eruption processes and increasingly sophisticated forecasts. Laboratory and numerical experiments are elucidating seismo-acoustic source processes in volcanic fluid systems, and are observationally constrained by increasingly dense geophysical field deployments taking advantage of low-power, compact broadband, and nodal technologies. In recent years, the fields of volcano geodesy, seismology, and acoustics (both atmospheric infrasound and ocean hydroacoustics) are increasingly merging. Despite vast progress over the past century, major questions remain regarding source processes, patterns of volcano-seismic unrest, internal volcanic structure, and the relationship between seismic unrest and volcanic processes.
... In this study, I examined the year before and the year after the Mw 7.8 April 16 th 2016 Pedernales earthquake, a time during which several seismic networks covered the region. The Permanent National Seismic Network of Ecuador (RENSIG) was active during the interseismic period and throughout the postseismic period (Alvarado et al., 2018). In 2018, this network was composed of 65 stations (Figure SB.1A) with very broadband, broadband, and short-period sensors. ...
... Additionally, Ecuador has a Permanent Strong Motion Network (RENAC) composed of 117 strong motion sensors, primarily located in densely populated areas and areas with a high historical seismic hazard (Figure SB.1B). It was also in place before and after the Pedernales earthquake (Alvarado et al., 2018). Finally, in response to the April 2016 mainshock, there was an effort to better cover the area through an international temporary deployment of seismic stations, which was supported by the Instituto Geofísico at Figure 28D. ...
... To extract repeating earthquakes occurring during the postseismic phase of the Pedernales earthquake, we use both the permanent seismic network in place in Ecuador (Alvarado et al., 2018), and the one-year temporary deployment of land and ocean bottom seismic (OBS) stations deployed in the aftermath of the Pedernales earthquake Meltzer et al., 2019). We examine 14 months of postseismic data, as well as 12 months of interseismic data. ...
The Ecuador-Colombian subduction zone has hosted a series of large subduction earthquakes over the course of the 20th century. This earthquake sequence started in 1906 with a Mw 8.4-8.8 earthquake, which ruptured a 200-500 km long segment of the megathrust. It was followed by three large earthquakes that broke, from south to north, portions already contained in the 1906 rupture. These earthquakes occurred in 1942 (Mw=7.8), 1958 (Mw=7.6) and 1979 (Mw=8.2), respectively. In 2016, the Pedernales earthquake re-ruptured the 1942 coseismic region, possibly starting a new cascade of large events.The Pedernales earthquake and its aftershocks, recorded thanks to the international deployment of seismic stations in the months following the mainshock, provide an opportunity to better understand the seismotectonic processes that occur in the region. This thesis will focus primarily on the interactions between seismicity and aseismic slip, and on the influence of the structure of the megathrust on the seismic activity.For this purpose, a catalogue of repeating earthquakes was created by correlating the existing aftershock catalogue. The families of repeating earthquakes were then completed using template-matching to find missing events. Repeating earthquakes were then relocated in a 1D model, first using manual picks and then using differential times from correlations. Finally, source properties were determined for a portion of the aftershock catalogue.Repeating earthquakes in Ecuador occur primarily within larger aftershock clusters situated at the edge of the main afterslip regions. Additionally, the slip associated with individual repeating earthquake families seems to have an indirect link to the slip modelled using GPS data. Indeed, family slip appears heterogeneous, suggesting perhaps a more complex link between afterslip and repeating earthquakes, and likely reflecting the complexity of the megathrust structure.Additionally, the study of source properties of Pedernales aftershocks reveals a segmentation of the subduction zone with distance to the trench. Stress drops near the trench are low, and decrease with time during the postseismic period, as observed within families of repeating earthquakes. This is probably due to a variation in pore fluid pressure, which is likely very high near the trench, and which plays a crucial role in seismogenesis in the region.
