Sandro Vaca

• Seismologist at National Polytechnic School

The 2019/05/26 Northern Peru earthquake (Mw=8) is a major intermediate-depth earthquake that occurred close to the eastern edge of the Nazca slab flat area. We analyze its rupture process using high-frequency back-projection and seismo-geodetic broadband inversion. The latter approach shows that the earthquake propagated with almost purely normal f...

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...

Megathrust ruptures and the ensuing postseismic deformation cause stress changes that may induce seismicity on upper plate crustal faults far from the coseismic rupture area. In this study, we analyze seismic swarms that occurred in the north Ecuador area of Esmeraldas, beginning two months after the 2016 Mw 7.8 Pedernales, Ecuador megathrust earth...

In the paper entitled “Two independent real-time precursors of the 7.8 M earthquake in Ecuador based on radioactive and geodetic processes – Powerful tools for an early warning system”, Toulkeridis et al. (2019) claim that they found radiation and GPS signal anomalies before the April 16th 2016 Pedernales earthquake (Ecuador) and that their finding...

La zona de Punta Galera- Mompiche (PGMZ), se encuentra en el norte de la margen ecuatoriana (latitudes: 0.3° N y 1. 2° N y longitudes: 80.4° W y 79.7° W). PGMZ está afectada por recurrentes enjambres sísmicos, que se asocian a la ocurrencia de “sismos lentos” (slow slip events, SSE). Posterior al sismo de Pedernales del 16 de abril de 2016 (Mw 7.8)...

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...

In the paper entitled “Two independent real-time precursors of the 7.8 M earthquake in Ecuador based on radioactive and geodetic processes – Powerful tools for an early warning system”, Toulkeridis et al. (2019) claim that they found radiation and GPS signal anomalies before the April 16th 2016 Pedernales earthquake (Ecuador) and that their finding...

The recent development of a national seismic broadband network in Ecuador enables us to determine a comprehensive catalog of earthquake focal mechanisms at the country-scale. Using a waveform inversion technique accounting for the spatially variable seismic velocity structure across the country, we provide location, depth, focal mechanism and seism...

El Reventador volcano, 100 km East of Quito, Ecuador, experienced a rapid onset VEI 4 eruption in November 2002. The last 15 years of intermittent periods of explosive and effusive activity continues to the present. Since 2012 there has been a different pattern in the type of events registered, specifically with an increase in processes associated...

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...

At subduction zones, transient aseismic slip occurs either as afterslip following a large earthquake or as episodic slow slip events during the interseismic period. Afterslip and slow slip events are usually considered as distinct processes occurring on separate fault areas governed by different frictional properties. Continuous GPS (Global Positio...

The northern Ecuador segment of the Nazca/South America subduction zone shows spatially heterogeneous interseismic coupling. Two highly coupled zones (0.4° S–0.35° N and 0.8° N–4.0° N) are separated by a low coupled area, hereafter referred to as the Punta Galera-Mompiche Zone (PGMZ). Large interplate earthquakes repeatedly occurred within the coup...

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....

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...