Susan Beck

• University of Arizona

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....

The East Anatolian Fault Zone (EAFZ) is a plate-bounding strike-slip fault capable of hosting large earthquakes, as demonstrated by the extremely damaging February 2023 Mw 7.8 and Mw 7.7 mainshocks of the Kahramanmaraş earthquake sequence. Deformation related to this boundary, part of the Anatolia-Arabia-Africa (A3) Triple Junction, is diffuse, as...

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...

Monitoring variations in seismic velocities surrounding active volcanoes provides insights into crustal deformation caused by eruptions and earthquakes. Turrialba volcano in Costa Rica has been erupting sporadically since 2010 and experienced a local seismic swarm in 2016, including the Mw 5.5 Capellades earthquake. It is thus an ideal natural labo...

Lateral movement of lithospheric fragments along strike-slip faults in response to collision (escape tectonics) has characterized convergent settings since the onset of plate tectonics and is a mechanism for the formation of new plates. The Anatolian plate was created by the sequential connection of strike-slip faults following ≥10 m.y. of distribu...

Seamounts and ridges are often invoked to explain subduction-related phenomena, but the extent of their involvement remains controversial. An analysis of seismicity in the region of the Pampean flat slab through an application of an automated catalogue generation algorithm resulted in 143,716 local earthquake hypocenters, 35,924 of which are associ...

Plain Language Summary The subducting African Plate in the easternmost Mediterranean has been tearing beneath central Turkey as the region switches from subduction to collision. This area provides one of the best chances to study how tearing of a subducting plate impacts patterns of mantle flow during the last stages of subduction. We study mantle...

The Nazca plate subducting beneath South America makes the 660 km discontinuity deeper and the mantle transition zone (MTZ) thicker under the continent. MTZ variations are often associated with mantle temperature and, therefore, can help confirm the slab position at greater depths. Recent P- and S-wave tomography results show the Nazca plate, near...

We present a new P‐wave seismic tomographic model for the region of the Paraná Basin and surroundings using a multiple‐frequency approach, providing better resolution than previous regional studies. We processed a total of 62,692 cross‐correlation delays for P, PKIKP, PcP, and PP phases distributed among 1,081 events using six different central fre...

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...

We performed shear wave splitting analyses to investigate seismic anisotropy across the northern extent of the Peruvian flat-slab subduction region. We used core-mantle refracted SKS, SKKS and PKS phases from teleseismic events (88° > Δ < 150°) recorded at 45 broadband seismic stations from the Peruvian permanent and portable seismic networks as we...

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...

The Andean Subduction Zone is one of the longest continuous subduction zones on Earth. The relative simplicity of the two-plate system has makes it an ideal natural laboratory to study the dynamics in subduction zones. We measure teleseismic S and SKS travel-time residuals at > 1,000 seismic stations that have been deployed across South America ove...

The Ecuadorian forearc is a complex region of accreted terranes with a history of large megathrust earthquakes. Most recently, a M w 7.8 megathrust earthquake ruptured the plate boundary offshore of Pedernales, Ecuador on 16 April 2016. Following this event, an international collaboration arranged by the Instituto Geofisico at the Escuela Politécni...

Observations of shear wave splitting have provided constraints on patterns of deformation in the mantle in a variety of tectonic settings, including those with complex dynamics such as subduction zones. The South American subduction system is characterized by the longest laterally continuous subducting slab present today. As such, it represents an...

The occurrence of intermediate depth seismicity (70–300 km) is commonly attributed to the dehydration of hydrous phases within the downgoing oceanic plate. While some water is incorporated into the oceanic crust at formation, a significant amount of water is introduced into the plate immediately before subduction along outer-rise faults. These faul...

The Andean subduction zone is an excellent place to study deformation within a subducting slab as a function of depth, owing to the varying and well‐resolved geometry of the subducting Nazca slab beneath South America. Here we combine the results of source‐side shear‐wave splitting with the latest regional tomography model to isolate intra‐slab ray...

Nazca subduction beneath South America is one of our best modern examples of long‐lived ocean‐continent subduction on the planet, serving as a foundation for our understanding of subduction processes. Within that framework, persistent heterogeneities at a range of scales in both the South America and Nazca plates is difficult to reconcile without d...

The heterogeneous seafloor topography of the Nazca Plate as it enters the Ecuador subduction zone provides an opportunity to document the influence of seafloor roughness on slip behavior and megathrust rupture. The 2016 Mw 7.8 Pedernales Ecuador earthquake was followed by a rich and active postseismic sequence. An internationally coordinated rapid...

The Ecuadorian convergent margin has experienced many large mega-thrust earthquakes in the past century, beginning with a 1906 event that propagated along as much as 500 km of the plate interface. Many subsections of the 1906 rupture area have subsequently produced Mw ≥ 7.7 events, culminating in the 16 April 2016, Mw 7.8 Pedernales earthquake. Int...

We obtain earthquake locations and a detailed three-dimensional velocity model of the flat slab subduction zone in west-central Argentina (latitudes: 32-30°S and longitudes: 70-66°W) using a regional-scale double-difference tomography algorithm with earthquake data recorded by the SIEMBRA (2007–2009) and ESP (2008–2010) broadband seismic networks....

Subduction along the active margin of a continental plate occurs in a context where the overriding plate's crust and lithospheric mantle may contain inherited structures significantly predating the present tectonic conditions of the margin. These structures are persistent over very long-term time scales (>10⁵ to >10⁶ years) and are thought to play...

On April 16th 2016 a Mw 7.8 earthquake ruptured the central coastal segment of the Ecuadorian subduction zone. Shortly after the earthquake, the Institute Geofisico de la Escuela Politecnica Nacional of Ecuador, together with several international institutions deployed a dense, temporary seismic network to accurately categorize the post-seismic aft...

We characterise the aftershock sequence following the 2016 Mw=7.8 Pedernales earthquake. More than 10,000 events were detected and located, with magnitudes up to 6.9. Most of the aftershock seismicity results from interplate thrust faulting, but we also observe a few normal and strike-slip mechanisms. Seismicity extends for more than 300 km along s...

We characterise the aftershock sequence following the 2016 Mw=7.8 Pedernales earthquake. More than 10,000 events were detected and located, with magnitudes up to 6.9. Most of the aftershock seismicity results from interplate thrust faulting, but we also observe a few normal and strike-slip mechanisms. Seismicity extends for more than 300 km along s...

The April 2016 Pedernales earthquake ruptured a 100 km by 40 km segment of the subduction zone along the coast of Ecuador in an M-w 7.8 megathrust event east of the intersection of the Carnegie ridge with the trench. This portion of the subduction zone has ruptured on decadal time scales in similar size and larger earthquakes, and exhibits a range...

Subduction systems play a key role in plate tectonics, but the deformation of the crust and uppermost mantle during continental subduction remains poorly understood. Observations of seismic anisotropy can provide constraints on dynamic processes in the crust and uppermost mantle in subduction systems. The subduction zone beneath Peru and Bolivia, w...

Using finite-frequency teleseismic P-wave tomography, we developed a new three-dimensional (3-D) velocity model of the mantle beneath Anatolia down to 900 km depth that reveals the structure and behavior of the subducting African lithosphere beneath three convergent domains of Anatolia: the Aegean, Cyprean, and Bitlis-Zagros domains. The Aegean sla...

The Central Andes are characterized by one of the largest orogenic plateaus worldwide. As a result, they are home to some of the thickest continental crust observed today (up to ~75-km thick). Understanding the response of the crust to such overthickening provides insights into the ductile behavior of the midcrust and lower crust. One of the best t...

Foreland deformation has long been associated with flat-slab subduction, but the precise mechanism linking these two processes remains unclear. One example of foreland deformation corresponding in space and time to flat subduction is the Fitzcarrald Arch, a broad NE-SW trending topographically high feature covering an area of >4 × 10⁵ km² in the Pe...

Beneath much of Peru lies the largest region of flat-slab subduction in the world today. The origins and dynamics of the Peruvian flat-slab however remain elusive, particularly in the north away from the Nazca Ridge. Studies of seismic anisotropy can potentially provide us with insight into the dynamics of recent and past deformational processes in...

The central Anatolian plateau in Turkey is a region with a long history of subduction, continental collision, accretion of continental fragments, and slab tearing and/or breakoffand tectonic escape. Central Anatolia is currently characterized as a nascent plateau with widespread Neogene volcanism and predominantly transtensional deformation. To elu...

Subduction beneath central Anatolia represents the transition between continuous subduction along the Aegean trench in the west and slab break-off and/or subduction termination at the Arabian-Eurasian collision zone in the east. Using recently collected seismic data from the Continental Dynamics-Central Anatolian Tectonics project alongside a newly...

The role of magmatic processes as a significant mechanism for the generation of voluminous silicic crust and the development of Cordilleran plateaus remains a lingering question in part because of the inherent difficulty in quantifying plutonic volumes. Despite this difficulty, a growing body of independently measured plutonic-to-volcanic ratios su...

A tear in the subducting Nazca slab is located between the end of the Pampean flat slab and normally subducting oceanic lithosphere. Tomographic studies suggest mantle material flows through this opening. The best way to probe this hypothesis is through observations of seismic anisotropy, such as shear wave splitting. We examine patterns of shear w...

Flat or near-horizontal subduction of oceanic lithosphere has been an important tectonic process both currently and in the geologic past. Subduction of the aseismic Nazca Ridge beneath South America has been associated with the onset of flat subduction and the termination of arc volcanism in Peru, making it an ideal place to study flat-slab subduct...

Current end-member models for the geodynamic evolution of orogenic plateaus predict (a) slow and steady rise during crustal shortening and ablative subduction (i.e., continuous removal) of the lower lithosphere or (b) rapid surface uplift following shortening, which is associated with punctuated removal of dense lower lithosphere and/or lower crust...

We present new tomographic models of the Nazca slab under South America from 6°S to 32°S, and from 95 km to lower mantle (895 km) depths. By combining data from 14 separate networks in the central Andes, we use finite-frequency teleseismic P-wave tomography to image the Nazca slab from the upper mantle into the mantle transition zone (MTZ) and the...

Seismic anisotropy has been documented in many portions of the lowermost mantle, with particularly strong anisotropy thought to be present along the edges of Large Low Shear Velocity Provinces (LLSVPs). The region surrounding the Pacific LLSVP, however, has not yet been studied extensively in terms of its anisotropic structure. In this study we use...

Slow seismic velocity anomalies are commonly imaged beneath subducting slabs in tomographic studies, yet a unifying explanation for their distribution has not been agreed upon. In South America two such anomalies have been imaged associated with subduction of the Nazca Ridge in Peru and the Juan Fernández Ridge in Chile. Here we present new seismic...

Despite significant progress toward understanding the kinematics of modern tectonic escape in Anatolia, considerable uncertainty remains regarding the dynamics of the transition from collision to escape. Because of the relatively small size of the Anatolia microplate, regional-scale studies spanning the plate margins and interior are well-suited to...

In this study, we present results from teleseismic receiver functions, in order to investigate the crustal thickness and Vp/Vs ratio beneath northern Peru. A total number of 981 receiver functions were analyzed, from data recorded by 28 broadband seismic stations from the Peruvian permanent seismic network, the regional temporary SisNort network an...

Subduction systems play a key role in plate tectonics, but the deformation of the crust and uppermost mantle during subduction and orogenesis in continental subduction systems remains poorly understood. Observations of seismic anisotropy can provide important constraints on dynamic processes in the crust and uppermost mantle in subduction systems....

The Puna Plateau of the Central Andes is a well-suited location to investigate the processes associated with the tectono-magmatic development of a Cordilleran system. These processes include long-lived subduction (including shallow and steep phases), substantial crustal thickening, the emplacement of large volumes of igneous rocks, and probably del...

The Central Andean Plateau (CAP), as defined by elevations in excess of 3 km, extends over 1,800 km along the active South American Cordilleran margin making it the second largest active orogenic plateau on Earth. The uplift history of this high Plateau, with an average elevation around 4 km above sea level, remains uncertain as paleoelevation stud...

The Altiplano-Puna Magma Body (APMB) in the Central Andes is the largest imaged magma reservoir on Earth, and is located within the second highest orogenic plateau on Earth, the Altiplano-Puna. Although the APMB is a first-order geologic feature similar to the Sierra Nevada batholith, its role in the surface uplift history of the Central Andes rema...

Supplementary Figures 1-2, Supplementary Tables 1-2 and Supplementary References.

The effects of complex slab geometries on the surrounding mantle flow field are still poorly understood. Here we combine shear wave velocity structure with Rayleigh wave phase anisotropy to examine these effects in southern Peru, where the slab changes its geometry from steep to flat. To the south, where the slab subducts steeply, we find trench-pa...

In the flat slab region of the South Central Andes (∼31–32 • S), geological observations suggest that the regional crustal structure is inherited from the accretion of different terranes during the Ordovician. These structures were later reactivated, first in extension during the Triassic and later in compression during the Andean uplift since the...

The Central Andean Plateau, the second-highest plateau on Earth, overlies the subduction of the Nazca Plate beneath the central portion of South America. The origin of the high topography remains poorly understood, and this puzzle is intimately tied to unanswered questions about processes in the upper mantle, including possible removal of the overr...

We have determined the Wadati–Benioff Zone seismicity and state of stress of the subducting Nazca slab beneath central and southern Peru using data from three recently deployed local seismic networks. Our relocated hypocenters are consistent with a flat slab geometry that is shallowest near the Nazca Ridge, and changes from steep to normal without...

The Central Andean Plateau (15°–27°S) is a high plateau in excess of 3 km elevation, associated with thickened crust along the western edge of the South America plate, in the convergent margin between the subducting Nazca plate and the Brazilian craton. We have calculated receiver functions using seismic data from a recent portable deployment of br...

Ambient Noise Tomography Workshop (MIMOSA); Tucson, Arizona, 17–23 January 2016 https://eos.org/meeting-reports/extending-recent-seismic-imaging-successes-to-south-america

Two arrays of broad-band seismic stations were deployed in the north central Andes between 8° and 21°S, the CAUGHT array over the normally subducting slab in northwestern Bolivia and southern Peru, and the PULSE array over the southern part of the Peruvian flat slab where the Nazca Ridge is subducting under South America. We apply finite frequency...

The role of magmatic processes (specifically in situ continental arcs) has a long history of being invoked or dismissed as a significant mechanism for contributing to the evolution of high elevation plateaus in cordilleran systems. One current prevailing view is that tectonic shorting (with minor magmatic addition) is sufficient to account for near...

Central Anatolia, Uplift, Crustal Structure, Receiver function

Within oceanic lithosphere a fossilized fabric is often preserved originating from the time of plate formation. Such fabric is thought to form at the mid-ocean ridge when olivine crystals align with the direction of plate spreading(1,2). It is unclear, however, whether this fossil fabric is preserved within slabs during subduction or overprinted by...

We present a new approach to the joint inversion of surface wave dispersion data and receiver functions by utilizing Common Conversion Point (CCP) stacking to reconcile the different sampling domains of the two datasets. Utilizing CCP stacking allows us to suppress noise in the data by waveform stacking, and correct for backazimuthal variations and...

Flat-slab subduction occurs when the descending plate becomes horizontal at some depth before resuming its descent into the mantle. It is often proposed as a mechanism for the uplifting of deep crustal rocks (‘thick-skinned’ deformation) far from plate boundaries, and for causing unusual patterns of volcanism, as far back as the Proterozoic eon1. F...

In the central Andes, the Nazca plate displays large along strike variations in dip with a near horizontal subduction angle between 28 and 32°S referred to the Pampean flat slab segment. The upper plate above the Pampean flat slab has high rates of crustal seismicity and active basement cored uplifts. The SIEMBRA experiment, a 43-broad-band-seismic...

Paleoelevation histories from the central Andes in Bolivia have suggested that the geodynamic evolution of the region has been punctuated by periods of large-scale lithospheric removal that drive rapid increases in elevation at the surface. Here, we evaluate viable times and locations of material loss using a map-view reconstruction of the Bolivian...

At ~31ºS, The subduction of the Nazca plate under the South American plate presents along strike variations of the dip angle referred to the Chilean/Pampean flat slab. In this region, the Andean backarc displays a series of foreland uplifts corresponding to the thin-skinned Precordillera to the west and the basement cored Sierras Pampeanas ranges t...

The Anatolian Plate is composed of different lithospheric blocks and ribbon continents amalgamated during the closure of the Paleotethys Ocean and Neotethys Ocean along a subduction margin. Using ambient noise tomography, we investigate the crustal and uppermost mantle shear wave velocity structure of the Anatolian Plate. A total of 215 broad-band...

The Peruvian flat slab is by far the largest region of flat subduction in the world today, but aspects of its structure and dynamics remain poorly understood. In particular, questions remain over whether the relatively narrow Nazca Ridge subducting beneath southern Peru provides dynamic support for the flat slab or it is just a passive feature. We...

Lithospheric foundering or delamination has been long recognized as an important process in the formation of the Andes, but the scale, timing, and surface uplift consequences remain controversial. We use recently completed ambient noise tomography and finite-frequency P-wave tomography results and other geologic and geophysical information to ident...

Flattening of the subducting plate has been linked to the formation of various geological features, including basement-cored uplifts, the cessation of arc volcanism, ignimbrite flare-ups, and the formation of high plateaus and ore deposits [Humphreys et al., 2003; Gutscher et al., 2000; Rosenbaum et al., 2005]. However, the mechanism responsible fo...

Western Anatolia is one of the most seismically active regions in the world, undergoing broad N-S extension associated with the rollback of the Aegean slab in the south. This region is characterized by high heat-flow, recent volcanism, and core-complex formation. We use >3500 receiver functions from a dense array of 47 stations located in western T...

Located in the central Andes, the Altiplano-Puna Volcanic Complex (APVC) is the location of an 11–1 Ma silicic volcanic field, one of the largest and youngest on Earth. Yet its magmatic/plutonic underpinnings have been seismically investigated in only a few widely spaced locations. Previous studies have identified an extensive (∼60,000 km2) low-vel...

Flat slab subduction has long been considered as a potential contributing factor in the formation of inland basement cored uplifts, volcanic sweeps and gaps, and widespread ignimbrite volcanism. However, the processes responsible for the formation of flat slabs are poorly constrained. This is of particular importance when evaluating the putative Fa...

After a long quiet period for earthquake activity with magnitude greater than 8.5, several great subduction megathrust earthquakes occurred during the past decade: Sumatra in 2004 and 2005, Chile in 2010, and Japan in 2011. Each of these events caused loss of life and damage to critical infrastructure on an enormous scale. And, in April, a Mw 8.2 e...

The dynamics of flat-subduction, particularly the interaction between a flat slab and the overriding plate, are poorly understood. Here we study the (seismically) anisotropic properties and deformational regime of the mantle directly above the Peruvian flat-slab. We analyze shear wave splitting from 370 local S events at 49 stations across southern...