Patricia Ann Mothes

Escuela Politécnica Nacional | EPN · Instituto Geofísico

In the Northern Andes, partitioning of oblique subduction of the Nazca plate beneath the South American continent induces a northeastward motion of the North Andean Sliver. The strain resulting from this motion is absorbed by crustal faults, which have produced magnitude 7 + earthquakes historically in the Andean Cordillera of Ecuador and southern...

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 a...

We report sustained uplift throughout Volcan Sangay’s most recent period of eruption (2019–22), moderated only by transient excursions during some of its largest explosions. Volcan Sangay (Amazonia, Ecuador), has been erupting since 2019, impacting both local communities and distant cities with ash fall and lahars. We analyzed ascending and descend...

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...

We explore how variation of slip rates in fault source models affect computed earthquake rates of the Pallatanga–Puna fault system in Ecuador. Determining which slip rates best represent fault-zone seismicity is vital for use in probabilistic seismic hazard assessment (PSHA). However, given the variable spatial and temporal scales slip rates are me...

Shallow magmatic reservoirs that produce measurable volcanic surface deformation are often considered as discrete independent systems. However, petrological analyses of erupted products suggest that these may be the shallowest expression of extensive, heterogeneous magmatic systems that we show may be interconnected. We analyse time series of satel...

Fringe Meeting in Leeds in Sept. 2023. Talk on Chiles-Potrerillos ground deformation.

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 be...

Identifying the sources of distal tephra in marine sediments or polar ice provides clues on the dynamic and large-scale impact of major volcanic eruptions. However, determination of the volcanic source of distal tephra is challenging due to size-dependent fractionation during atmospheric transport that modifies the mineral, chemical and even isotop...

In 1999–2001, Guagua Pichincha volcano, Ecuador, produced a series of cyclic explosive and effusive eruptions. Rock samples, including dense blocks and pumiceous clasts collected during the eruption sequence, and ballistic bombs later collected from the crater floor, provide information about magma storage, ascent, decompression, degassing, repress...

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...

En 1698, registros históricos narran la ocurrencia de un gran terremoto (7.3 MIC) a los pies del volcán Carihuairazo, Ecuador. El terremoto destruyó la antigua ciudad de Ambato y desencadenó enormes flujos de lodo que descendieron por el río Ambato. Los flujos de lodo enterraron las entonces ruinas de la ciudad y a los sobrevivientes del terremoto....

On 2 December, 2021 we recorded a sequence of drumbeat seismic events at Sangay volcano. This sequence lasted several hours and resulted in two explosive emissions whose eruptive columns reached 9 km above crater. Unexpectedly, these explosions did not produce any ash fallout in the inhabited areas around the volcano. This drumbeat sequence was pro...

Tephra layers preserved in marine sediments are strong tools to study the frequency, magnitude and source of past major explosive eruptions. Thirty‐seven volcanoes from the Ecuadorian and Colombian arc, in the northern Andes, experienced at least one eruption during the Holocene. The volcanic hazard is therefore particularly high for the populated...

We use new GPS data to determine an updated Euler pole describing the present-day motion of the oceanic Nazca plate. Our solution includes continuous GPS (cGPS) measurements at Malpelo Island offshore Colombia, two sites in the Galapagos archipelago, Easter Island and Salas y Gomez Island in the western part of the plate and Robinson Crusoe Island...

Reference ecosystems used in tropical forest restoration lack the temporal dimension required to characterise a mature or intact vegetation community. Here we provide a practical ‘palaeo-reference ecosystem’ for the eastern Andean forests of Ecuador to complement the standard ‘reference ecosystem’ approach. Pollen assemblages from sedimentary archi...

Using recent advancements in high-performance computing data assimilation to combine satellite InSAR data with numerical models, the prolonged unrest of the Sierra Negra volcano in the Galápagos was tracked to provide a fortuitous, but successful, forecast 5 months in advance of the 26 June 2018 eruption. Subsequent numerical simulations reveal tha...

For the first time in decades, a sudden increase in seismicity has been observed and monitored at Cayambe volcano in Ecuador, in 2016. This seismic unrest, which occurred a few months after the April 2016, Mw 7.8 Pedernales subduction earthquake, has raised many questions, especially as there is no record of recent eruptions at Cayambe volcano. Her...

New obsidian samples (fragments of pebbles and fakes), mixed with ceramic sherds, were found in 10–25 cm cm deep excavations in the Alto Coca Reserve (Napo Province, Ecuador) upon a fat platform on a ridgetop when digging postholes and drainage ditches. Charcoal associated with both obsidian and pottery fragments, attesting to a possible settlement...

Noventa y ocho volcanes cuaternarios han sido identificados en los Andes ecuatorianos y Galápagos de los cualesnueve han experimentado erupciones al menos una vez en los últimos veinte años. Adicionalmente, alrededor del35 % de la población ecuatoriana vive en zonas que podrían ser afectadas durante futuras erupciones. El InstitutoGeofísico de la E...

Ninety-eight Quaternary volcanoes have been identified in the Ecuadorian Andes and the Galápagos Islands, from them, nine experienced at least one eruption in the last twenty years. Additionally, about 35 % of the Ecuadorian population live in areas that could be affected by future volcanic eruptions. The Instituto Geofísico of the Escuela Politécn...

Sumaco is a stratovolcano located in the northern SubAndean zone of Ecuador, 105 km east of Quito. The flanks of Sumaco are jungle-covered, and scarce outcrops are found along stream banks, trails and, in quarries. Based on our field studies, eruptions of Sumaco during the historical era were associated with small-scale Strombolian activity. Earlie...

Abstract for the Fringe meeting 31 May -04 June 2021 (Virtual)

The Northern Andes of Ecuador contain some of the most active volcanic systems in the Andes and extend over a broad region from the Western Cordillera to the Subandean Zone. While it is known that the arc straddles a range of basement compositions, from accreted mafic oceanic terranes in the west to silicic continental terranes in the east, the det...

The mid-elevation settings of the Andes are important biodiversity hotspots, yet little is known of their long-term ecology or environmental change. Here, we assess 30,000 years of landscape and vegetation dynamics on an alluvial terrace located in a mid-elevation valley of the Ecuadorian Andes (Campo Libre). We used loss-on-ignition and particle s...

Sangay is one of the most active volcanoes in the world. Its eruptions were first recorded by Spanish priests in 1628, and since 2010 it has displayed VEI 1–2 level eruptive activity about every two years. Its most recent eruptive phase began on May 7, 2019, and has continued until the present. While most eruptive products do not impact inhabited a...

The interaction of volcanic activity with snow and ice bodies can cause serious hazards and risks. These interactions relate to enhanced heat flow, tephra in contact with the ice and snow resulting in the alteration of surficial ablation, and interaction with pyroclastic flows and incandescent materials. Such interactions can result in the formatio...

Breve descripción geológica y proceso de formación.

Determining the lithology, extent, origin, and age of hummocks can be challenging, especially if these are covered by successive deposits and lush vegetation. At Chalupas caldera, a late-Pleistocene silicic center that lies astride the Eastern Cordillera of northern Ecuador, we have tried to overcome these difficulties by combining geological obser...

BREVE RESUMEN DE SU HISTORIA, ACTIVIDAD ERUPTIVA Y AMENAZAS POTENCIALES

Unparalleled levels of tropical forest restoration are required to counter decades of deforestation, minimise losses in biodiversity and aid in combating climate change. Restoration projects which disregard the temporal dimension (decades-centuries) risk restoring a degraded ecosystem, as our expectations of what is ‘normal’ diminish over generatio...

The newest version of the Potential Volcanic Hazards Map of Guagua Pichincha Volcano (Third Edition) IG-EPN/IGM

Highly periodic, repetitive long‐period (LP) earthquakes, known as “drumbeats,” have been observed at a range of volcanoes, typically during the ascent of degassed magma. Accelerating rates of drumbeats have been reported before explosions and potentially offer forecasts of future activity. However, the broader phenomenology of drumbeats is poorly...

High rates of volcano surface deformation can be indicative of a forthcoming eruption, but can also relate to slope instability and possible flank collapse. Tungurahua volcano, Ecuador, has been persistently active since 1999 and has previously experienced catastrophic flank failures. During the ongoing eruptive activity, significant surface deform...

The 14 July 2013 Vulcanian explosion at Tungurahua occurred after two months of quiescence and was extremely powerful, generating some of the highest infrasound energies recorded worldwide. Here we report on how a combination of geophysical data, textural measurements, and physical and mechanical tests on eruptive products allowed us to determine t...

High-Rate (HR) GPS time series following the 2016 M-w 7.8 Pedernales earthquake suggest significant postseismic deformation occurring in the early postseismic period (i.e. first few hours after the earthquake) that is not resolved with daily GPS time series. To understand the characteristics of early postseismic deformation, and its relationship wi...

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...

Guagua Pichincha volcano (4784m a.s.l.) is the youngest part of the Pichincha Volcanic Complex, a potentially active volcano, located on the Western Cordillera of the Ecuadorian Andes. It is a compound stratovolcano located at 12 km W of Quito (capital of Ecuador, with population of 3 million peole). The youngest eruptive center in Guagua Pichincha...

On August 14, 2015 Cotopaxi Volcano (Ecuador) erupted with several phreatomagmatic explosions after nearly 135 years of quiescence. Unrest began in April 2015 with an increase in the number of daily seismic events and inflation of the flanks of the volcano. Time-lapse gravity measurements started at Cotopaxi volcano in June 2015. Although minor gra...

The understanding of magma ascent dynamics is essential in forecasting the scale, style and timing of volcanic eruptions. The monitoring of near-field deformation is widely used to gain insight into these dynamics, and has been linked to stress changes in the upper conduit. The ascent of magma through the conduit exerts shear stress on the conduit...

The Digital Elevation Model (DEM) is one of the most important inputs when working on computer simulations to define areas potentially affected by gravity-driven flow hazards. Sometimes there is only one DEM available in the study area, although nowadays the availability of several different DEMs of varying resolutions and precision is more frequen...

Cotopaxi is an active stratovolcano, located 60 km SE of Quito. During historical times, Cotopaxi experienced at least five eruptive cycles triggering major lahars which descended along all three main fluvial systems: Pita (north), Cutuchi (south) and Tambo-Tamboyaku (east). Northern and southern lahar deposits have been studied for decades, due to...

Lava flows pose a significant hazard to infrastructure and property located close to volcanoes, and understanding how flows advance is necessary to manage volcanic hazard during eruptions. Compared to low-silica basaltic flows, flows of andesitic composition are infrequently erupted and so relatively few studies of their characteristics and behavio...

We use GPS data of Ecuador's national continuous geodetic network to constrain ongoing post-seismic deformation associated with the destructive 2016 M w 7.8 Pedernales, Ecuador subduction earthquake. The main shock's occurrence produced a maximum co-seismic slip of 6 m with a southward rupture of 2 main asperities.

Since initiation three years ago the Ecuadorian Volcano Supersite, as approved by the Geohazard Supersite and Natural Laboratory Initiative (GSNL) has provided InSAR time series for analysis which has aided in monitoring 5 Ecuadorian volcanoes. Specifically imagery from the satellite systems Sentinel-1 of the European Space Agency, TerraSAR-X of th...

Displacement waveforms derived from Global Navigation Satellite System (GNSS) data have become more commonly used by seismologists in the past 15 yrs. Unlike strong‐motion accelerometer recordings that are affected by baseline offsets during very strong shaking, GNSS data record displacement with fidelity down to 0 Hz. Unfortunately, fully processe...

Changes in the pathway and timescale of magma ascent can be responsible for variations in eruptive style during long-lived eruptions, but are only documented at a small number of well-instrumented systems. Here we integrate PS-InSAR from high resolution TerraSAR-X radar imagery with continuous GPS data from 4 sites at Tungurahua volcano, Ecuador. O...

The Sub-Andean zone east of the Cordillera Real, Ecuador and out to the Amazon basin's western margin has been the depository of voluminous lahars related to volcanic activity in the Andean highlands. These lahars arrived to the Sub-Andean zone via gravitational transport through narrow river canyons and emplaced volumes surpassing several cubic ki...

Guagua Pichincha Volcano (GGP) is the active eruptive center closest to Quito and is located only 12 km SW of the city center. In 1999-2001 it had moderate eruptive activity (VEI 2) with the formation of eight domes that exploded, collapsed and formed ash columns that were directed to the W-NW and eastward, depositing two cm of ash over Quito. Due...

The Chalupas caldera is located atop the Eastern Cordillera of Ecuador, 80 km southeast of Quito. The caldera formed due to a major rhyolitic eruption (~100 km³ of magma) whose single-event evacuation caused the collapse. The tephra deposit from this eruption is the non-welded “Chalupas Ignimbrite” (~211 kyr) which flowed over 100 km distance in a...

European colonization of South America instigated a continental-scale depopulation of its indigenous peoples. The impact of depopulation on the tropical forests of South America varied across the continent. Furthermore, the role that indigenous peoples played in transforming the biodiverse tropical forests of the Andean–Amazonian corridor before AD...

Within Latin America, about 319 volcanoes have been active in the Holocene, but 202 of these volcanoes have no seismic, deformation or gas monitoring. Following the 2012 Santorini Report on satellite Earth Observation and Geohazards, the Committee on Earth Observation Satellites (CEOS) developed a 4-year pilot project (2013-2017) to demonstrate how...

Satellite-based measurements of synthetic aperture radar amplitude provide a method for monitoring volcanoes during unrest and eruptions even when visual observations are not possible, for example due to poor weather or at night, and when radar phase measurements are noisy or decorrelated. Here, we use high resolution radar amplitude images from th...

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 2015 reactivation of the Cotopaxi volcano urges us to understand the complex eruptive dynamics of Cotopaxi for better management of a potential major crisis in the near future. Cotopaxi has commonly transitioned from andesitic eruptions of strombolian style (lava flows and scoria ballistics) or nuées ardentes (pyroclastic flows and ash falls) t...

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...

Accelerating rates of quasi-periodic ‘drumbeat’ long period earthquakes (LPs) are commonly reported before eruptions at andesite and dacite volcanoes, and promise insights into the nature of fundamental pre-eruptive processes and improved eruption forecasts. Here we apply a new Bayesian MCMC gamma point process methodology to investigate an excepti...

Cyclic seismicity and ground deformation patterns are observed on many volcanoes worldwide where seismic swarms and the tilt of the volcanic flanks provide sensitive tools to assess the state of volcanic activity. Ground deformation at active volcanoes is often interpreted as pressure changes in a magmatic reservoir, and tilt is simply translated a...

Sumaco Volcano is located in the rear-arc of Ecuador and produces phonolitic alkaline lavas hosting a unique assemblage of minerals including haüyne and titanaugite. The most mafic lavas are picrobasalts that contain titanaugite as the primary mineral phase; the most evolved tephri-phonolite lavas contain titanaugite + anorthoclase + haüyne. Titana...

Aquatic ecosystems in the tropical Andes are under increasing pressure from human modification of the landscape (deforestation and dams) and climatic change (increase of extreme events and 1.5 °C on average temperatures are projected for AD 2100). However, the resilience of these ecosystems to perturbations is poorly understood. Here we use a multi...

Lava extrusion at erupting volcanoes causes rapid changes in topography and morphology on the order of tens or even hundreds of metres. Satellite radar provides a method for measuring changes in topographic height over a given time period to an accuracy of metres, either by measuring the width of radar shadow cast by steep sided features, or by mea...

Understanding the impact of landscape-scale disturbance events during the last glacial period is vital in accurately reconstructing the ecosystem dynamics of montane environments. Here, a sedimentary succession from the tropical montane cloud forest of the eastern Andean flank of Ecuador provides evidence of the role of non-climate drivers of veget...