Monica Segovia

• Seismologist at National Polytechnic School

The Ecuadorian Andes are a complex region characterized by accreted oceanic terranes driven by the ongoing subduction of the oceanic Nazca plate beneath South America. Present-day tectonics in Ecuador are linked to the downgoing plate geometry featuring the subduction of the aseismic, oceanic Carnegie Ridge, which is currently entering the trench....

Subduction zones generate the largest earthquakes on Earth, yet their detailed structure, and its influence on seismic and aseismic slip, remains poorly understood. Geological studies of fossil subduction zones characterize the seismogenic interface as a 100 m–1 km thick zone1, 2–3 in which deformation occurs mostly on metres-thick faults1,3, 4, 5–...

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-l...

The Instituto Geofísico (IG-EPN) was created in 1983 by faculty of the Escuela Politécnica Nacional, a public university in Quito, Ecuador, with the objective of assessing volcanic hazard in the country. Since then, the IG-EPN has established and developed an instrumental monitoring network and from 1999 has faced the eruption of five continental-a...

The Nazca-South America subduction zone in Ecuador is characterized by a complicated along-strike geometry as the slab transitions from flat slab subduction in the south, with the Peruvian flat slab, to what has been characterized as “normal” dipping subduction beneath central Ecuador. Plate convergence additionally changes south to north as the tr...

The Billecocha plateau (4000 m a.s.l.) lies in the high elevation Ecuadorian Andes volcanic arc. It overhangs by 2000 m above the interandean valley. Both the plateau and surrounding volcanoes are heavily affected by active faulting characterized by straight, sharp and discontinuous scarps within a 6 km wide and 24 km long corridor. Contrasting int...

Repeating earthquakes repeatedly rupture the same seismic asperity and are strongly linked to aseismic slip. Here, we study the repeating aftershocks of the April 16, 2016 MW 7.8 Pedernales earthquake in Ecuador, which generated a large amount of afterslip. Using temporary and permanent stations, we correlate waveforms from a one‐year catalog of af...

The Quito Fault System (QFS) is part of the Inter-Andean depression (ID) in Ecuador and extends from 0°N to 60 km southward along strike of the Western Cordillera. It consists of N-S striking, steep west-dipping blind thrusts. Quito megapolis and urban area lies at 2300 to 3200 meters above sea level and extends from the western flank of active Pic...

A temporary onshore-offshore seismic network deployed during the 2-year period of the Observación SISmológica en ECuador project provides a detailed and well-focused image of the seismicity for magnitudes as low as 2.1 at the Central Ecuadorian subduction zone. During this 2-year experiment, the shallow and locked subduction patch shows little evid...

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...

The continuous Global Positioning System (cGPS) network operating in the northern Andes (Ecuador and Colombia) for about a decade has the main objectives of quantifying interseismic coupling along the subduction interface, detecting occurrence of transient aseismic episodic slip, detailing the rupture kinematics of large earthquakes, recording long...

The central subduction zone of Ecuador is characterized by a highly coupled patch, no known large earthquakes and frequent seismic swarms, some of them associated to slow slip events (SSE). The earthquakes recorded on a temporal onshore-offshore network show an unprecedented image of the background seismicity and of several intense swarms in early...

Along the Ecuadorian margin, oblique subduction induces deformation of the overriding continental plate. For the last 15Ma, both exhumation and tectonic history of Ecuador suggest that the northeastward motion of the North Andean Sliver (NAS) was accompanied by an eastward migration of its eastern boundary and successive progressively narrowing res...

A dense GPS network deployed in Ecuador reveals a highly heterogeneous pattern of interseismic coupling confined in the first 35 km depth of the contact between the subducting oceanic Nazca plate and the North Andean Sliver. Interseismic models indicate that the coupling is weak and very shallow (0–15 km) in south Ecuador and increases northward, w...

[1] The Quito Fault System (QFS) extends over 60km along the Interandean Depression in northern Ecuador. Multidisciplinary studies support an interpretation in which two major contemporaneous fault systems affect Quaternary volcanoclastic deposits. Hanging paleovalleys and disruption of drainage networks attest to ongoing crustal deformation and up...

We document a one week long slow-slip event (SSE) with an equivalent moment magnitude of 6.0-6.3 which occurred in August 2010 below La Plata Island (Ecuador), south of the rupture area of the Mw=8.8 1906 megathrust earthquake. GPS data reveal that the SSE occurred at a depth of about 10km, within the downdip part of a shallow (<15km), isolated, lo...

Building a unified and homogeneous earthquake catalog is a preliminary step for estimating probabilistic seismic hazard in a country. Ecuador, a territory of similar to 600 km x 500 km, is characterized by an active seismicity, both in the shallow crust and in the subduction zone. Several international and local earthquake catalogs are available, c...

To improve earthquake location, we create a 3-D a priori P-wave velocity model (3-DVM) that approximates the large velocity variations of the Ecuadorian subduction system. The 3-DVM is constructed from the integration of geophysical and geological data that depend on the structural geometry and velocity properties of the crust and the upper mantle....

A seismic study of a segment of the convergent margin of Ecuador is presented. During the SISTEUR campaign a network of 24 Ocean Bottom Seismometers (OBS) was deployed on the Carnegie Ridge, one line along the main axes of the ridge and two lines across the strike of the edge of the ridge, during one month. This marine network was complemented with...

The subduction of the Nazca plate beneath South America has caused one of the largest megathrust earthquake sequence during the XXth century with three M>7.7 earthquakes that followed the great 1906 (Mw = 8.8) event. Better understanding the processes leading to the occurrence of large subduction earthquakes requires to monitor the ground motion ov...

In Ecuador, the Nazca plate is subducting beneath the North Andean Block. This subduction triggered, during the last century, 4 major earthquakes of magnitude greater than 7.7. Between 1994 and 2007, the Geophysical Institute (Escuela National Politecnica, Quito) recorded about 40 000 events in whole Ecuador ranging from Mb 1.5 to 6.9. Unfortunatel...

Ecuador has 55 active volcanoes in the northern half of the Ecuadorian Andes. There, consequences of active volcanism include ashfalls, pyroclastic flows (fast moving fluidized material of hot gas, ash, and rock), and lahars (mudflows), which result in serious damage locally and regionally and thus are of major concern to Ecuadorians. In particular...

The magnitude of an earthquake is a measure related to its energy. If a geographical region is selected for research, many earthquakes with differ-ent energies may appear during the study interval. An analysis of the distribution of magnitude values can be useful to understand some spatial and temporal characteristics of the region. Gutenberg & Ric...

With the deployment of the seismic network since 1990, in Ecuador has been identified several focus of seismic activity related with subduction zone, subducted plate and minor and major inland structures. The coastal zone of Ecuador has been affected by several 6.9 and greater subduction earthquakes. Since 1990, they have been noticed seismic swarm...

The city of Quito (1.5 million pop.), Ecuador, located in the interandean valley, is lirnited on the west side by Guagua Pichincha Volcano and on the east side by a series of slopes aligned NNE, in accordance with the Andean trend. This latter morphological feature is the superficial expression of the Quito Active Fault System. Since June 1998, an...

In front of the Ecuadorian coast, the Nazca plate subducts beneath the South America plate. This kind of limits between plates fail repeatedly in large earthquakes, moreover, important topographie features like the Carnegie Ridge in the Nazca Plate may produce strong coupling and the behavior of energy release may be very complex . So, studying the...

Guagua Pichincha volcano, located in the Western Cordillera of the Ecuadorian Andes, is one of the most dangerous active volcanoes in the country. It is located 12 km to the west of Quito (population 1.5 million). Guagua Pichincha has shown a progressive reactivation since its onset in 1981 that consists rnainly in phreatic explosions, shallow seis...

La ville de Quito est située sur une zone de forte activité sismique et volcanique, limitée à l'est par un système de plis et failles, alors qu'à l'ouest, la ville est bordée par le volcan Guagua Pichincha. Durant le deuxième semestre de 1998, un intense essaim sismique est apparu au nord de la ville de Quito, enregistrant plus de 4000 événements....

L'analyse des ondes P et SH de données télésismiques de large bande a permis de déterminer le mécanisme focal (proche de celui calculé par Harvard) et la durée de la rupture du séisme de Bahia de 1998 évaluée à 10 secondes. La localisation des répliques à partir d'enregistrements locaux et régionaux a permis de définir la zone de rupture, qui corre...

Depuis août 1998, le volcan Guagua Pichincha, situé dans la cordillère occidentale des Andes équatoriennes, montre une forte activité sismique et magmato-phréatique. Cependant, cette activité est instable dans le temps comme le montre les variations du facteur b. Ce comportement pourrait être en relation avec des changements du champs de contrainte...

At 01:51 on 3 October 1995 (UT) a Mw 6.8 earthquake located at 2.80°S, 77.96°W at a depth of 16 km occurred on the SE flank of Cutucu cordillera, a NNE-SSW Jurassic-Cretacic anticline, located on the western edge of the Subandean zone. While major shallow earthquakes occur in the coastal zone, the seismic hazard in the Subandean zone of Ecuador sho...

Depuis 1991, l'activité sismique en évènements LP du volcan Cotopaxi est continue. L'analyse de la distribution spatiale des séismes montre que ceux-ci sont situés à des profondeurs intermédiaires (8 à 18 km). De plus, la stabilité des paramètres tels que le contenu fréquentiel, la magnitude et la libération d'énergie montrent que l'activité LP est...

Le séisme de Macas, caractérisé par un mécanisme au foyer avec un plan nodal orienté N30E, s'est produit au niveau du bombement structural de Cutucu, sur la bordure occidentale de la zone subandine. Du 3 octobre au 31 décembre 1995, il a été enregistré environ 2100 répliques. Suite au séisme de 1987, le séisme de Macas met en valeur l'activité tect...