Steven W. Roecker

Verified

Steven verified their affiliation via an institutional email.

Learn more

Verified

Steven verified their affiliation via an institutional email.

Learn more

• PhD
• Professor at Rensselaer Polytechnic Institute

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 Tuina prospect is situated in northern Chile, approximately 50 km east of Calama in the Antofagasta Region. It lies within the Eocene-Oligocene metallogenic belt, which is home to world-class copper deposits, including Chuquicamata, El Abra, and Radomiro Tomic. To characterize the subsurface architecture, we deployed a temporary seismic network...

We present an updated and validated seismic catalog for the northern Fennoscandian region, focusing on postglacial faults from the Merasjärvi fault system in the southwest to the Iešjávri fault system in the northeast. This work involved a comprehensive review of continuous waveforms derived from open datasets from 2007 to 2015 and processed using...

Dozens of researchers deployed nearly 2,000 seismic stations—and a T-Rex—to better illuminate subsurface structure and magma storage below the summit of the highly active volcano.

The western South American margin is one of the most active on Earth. This region is home to a number of seismotectonic processes, including large megathrust and intraslab earthquakes, slow slip events, mountain building, and numerous large-scale crustal fault systems that extend for thousands of kilometers. The expressions of fractures, faulting a...

Recordings of earthquakes by a temporary deployment of 84 short period seismometers in northern Chile were used to derive regional 3D seismic velocity models for the Taltal segment. We used the Regressive ESTimator (REST) package for event detection and automatic onset estimation of P‐ and S‐wave arrival times to create an earthquake catalog with 2...

Plate motion obliquity along the dominantly transform Queen Charlotte plate boundary (QCPB) peaks offshore Haida Gwaii. To investigate the effects of obliquity on plate boundary deformation, we analyze continuous seismic waveforms from temporary and permanent stations from 1998 to 2020 to generate a catalog of ∼50,000 earthquakes across Haida Gwaii...

Progress on the seismic tomography for the 2014 M8.2 Iquique earthquake rupture area. Results show the performance of CORREL, an automatic onset detector for active source experiments. Furthermore, the detected arrival times were inverted to determine Vp and Vp/Vs models to characterize the margin in northern Chile.

Estimates of the onset times of P phases from active source experiments can effectively be used in developing wavespeed models, and the large number of recordings typical of such experiments incentivizes the development of automated approaches to generate these estimates. The simplicity and repeatability of an airgun source such as that used in the...

Seamounts and ridges are often invoked to explain subduction‐related phenomena such as flat slab generation, 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 catalog generation algorithm resulted in 35,924 well constrained local earthqu...

The Queen Charlotte plate boundary marks a transpressional system between the Pacific and North American plates, extending from offshore Haida Gwaii in Canada into southeastern Alaska. Using continuous seismic waveforms from temporary and permanent seismic networks from 1998–2020, we produced a comprehensive catalog of ~50,000 earthquakes across th...

The Queen Charlotte triple junction/Explorer microplate region offshore British Columbia, Canada, is marked by poorly understood and rapidly evolving microplate tectonics. Although the region hosts abundant seismicity, it has received relatively scant attention in recent years due to its remote, offshore location. We use the Regressive ESTimator (R...

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...

An essential part of the world's remaining mineral resources is expected to reside deep in the crust or under post-mineralization cover. For porphyry copper deposits, the world’s primary source of Cu, Mo, and Re, identifying the dynamic processes that control their emplacement in the upper crust can guide future exploration. Seismic tomography can...

Slow slip events in the northern Hikurangi margin of Aotearoa New Zealand occur every 18–24 months and last for several weeks before returning to average convergence rates of around 38 mm/yr. Along this plate boundary, the Hikurangi plateau subducts beneath the overlying Australian plate and slow slip events occur along their plate interface at dep...

Estimates of the onset times of P phases from active source experiments can effectively be used in developing wavespeed models, and the large number of recordings typical of such experiments incentivizes the development of automated approaches to generate these estimates. The simplicity and repeatability of an airgun source such as that used in the...

With the advancement of the use of geophysical methods in mining exploration, the possibility of restudying known mineral deposits that could have greater potential than that previously estimated is opening up, as is the case in the Maricunga Belt (MB), which is a metallogenic belt located east of Copiapó, Chile, with a length of 200 km and oriente...

Seismograms of about 12,000 aftershocks of the Mw6.7 Coquimbo-La Serena earthquake of 20 January 2019 that were recorded during six months by an array of 33 short-period seismic stations are used to generate wavespeed images of the subduction wedge beneath the Chilean forearc between 28.0°-30.6°S. This part of the margin is near the northern termin...

We analyze records of ambient seismicity from Central Chile to investigate mechanisms of tectonic erosion and accretion in an Andean margin. The seismograms were recorded by a temporary network of 39 stations deployed between 32.5°S and 34.0°S from April to November 2017. We employ an automatic earthquake catalogue generator to estimate 8463 P-wave...

We employ an automatic earthquake detection algorithm to seismic waveforms recorded between the years 2000 and 2020 in southwest British Columbia. 32,121 events which possess at least three paired P‐ and S‐wave arrival times are located, compared to 21,538 seismic events in the existing Geologic Survey of Canada catalog. This augmented catalog is e...

In southcentral Alaska, the Alaska‐Aleutian Wadati‐Benioff zone (WBZ) shows high seismicity rates west of 147°W. Further east, the Wrangell volcanic field (WVF) has some of the world's largest continental volcanoes but there is equivocal evidence for a WBZ. We deployed a dense seismometer array around the WVF between 2016 and 2018 and used the data...

We investigated the seismic velocity structure of the Hikurangi margin in New Zealand to uncover the physical features of the subduction zone and explore the relationships between microearthquake seismicity, seismic velocity structure, and slow slip events. Using local earthquake tomography with data collected from both temporary ocean bottom seism...

Double differencing of body-wave arrival times has proved to be a useful technique for increasing the resolution of earthquake locations and elastic wavespeed images, primarily because (1) differences in arrival times often can be determined with much greater precision than absolute onset times and (2) differencing reduces the effects of unknown, u...

Following the Mw 8.8 Maule megathrust earthquake that occurred on February 27, 2010, in central Chile, a sequence of normal faulting crustal earthquakes occurred close to the city of Pichilemu. This activity lasted several months and included two large events (Mw = 6.9 and Mw = 7.0) on March 11, 2010. An initial investigation of this activity analy...

Observations of travel time anomalies of inner core-sensitive PKPdf seismic body waves, as a function of path orientation with respect to the earth's rotation axis, have been interpreted as evidence of anisotropy in the inner core. Paths from earthquakes in the South Sandwich Islands to stations in Alaska show strongly anomalous travel times, with...

Aftershocks of the 16 September 2015 M8.3 Illapel earthquake in central Chile were recorded for a period of one year by the Chile-Illapel Aftershock Experiment (CHILLAX) seismic network. An initial catalog of about 100,000 events was generated by a novel automated picking algorithm that combines an auto-regressive detection/onset estimation method...

Plain Language Summary Earthquake locations are fundamental for understanding the physics of earthquakes, defining the orientations and geometries of faults that have slipped seismically, and assisting in seismic hazard forecasting and assessment. We have mapped the locations of approximately 2,700 of the largest aftershocks that followed the 14 No...

Strain in magmatic rifts is accommodated by both faulting and dike intrusion, but little is known of the frequency of dike intrusions in early-stage rifts. We use a new earthquake data set from a dense temporary seismic array (2013–2014) in the ~7-Myr-old Magadi-Natron-Manyara section of the East African Rift, which includes the carbonatitic Oldoin...

We present a joint analysis of newly acquired gravity and teleseismic data in the North Tanzanian Divergence, where the lithospheric break-up is at its earliest stage. The impact of a mantle upwelling in more mature branches of the East African Rift has been extensively studied at a lithospheric scale. However, few studies have been completed that...

One of the most devastating earthquakes in the last 100 years is the Ms 7.8 Tangshan intraplate earthquake occurred on 28 July 1976, caused more than 240,000 deaths, and razed the city of Tangshan. To investigate the possible dynamic mechanisms of the Tangshan earthquake, we conducted high-resolution seismic imaging with an extensive dataset of arr...

Rifting in a cratonic lithosphere is strongly controlled by several interacting processes including crust/mantle rheology, magmatism, inherited structure and stress regime. In order to better understand how these physical parameters interact, a 2 yr long seismological experiment has been carried out in the North Tanzanian Divergence (NTD), at the s...

We employ an empirical approach to study the phenomenon of surface wave mode conversion due to lateral heterogeneity, and, as an example, assess its impact on a specific waveform inversion methodology used for surface wave tomography. Finite difference modelling in 2-D media, using a method that allows modelling of a single surface wave mode at a t...

Although magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2-D studies. We analyze seismicity data from a 13 month, 39-station broadband seismic array to determine the role of magma intrusion on state-of-stress and strain localization, and their along-strike...

The Eastern Rift System (ERS) of northern Tanzania and southern Kenya, where a cratonic lithosphere is in the early stages of rifting, offers an ideal venue for investigating the roles of magma and other fluids in such an environment. To illuminate these roles, we jointly invert arrival times of locally recorded P and S body waves, phase delays of...

Rifting in a cratonic lithosphere is strongly controlled by several interacting processes including crust/mantle rheology, magmatism, inherited structure and stress regime. In order to better understand how these physical parameters interact, a 2 yr long seismological experiment has been carried out in the North Tanzanian Divergence (NTD), at the s...

The Deep Fault Drilling Project (DFDP) on the central Alpine Fault, South Island, New Zealand, has motivated a broad range of geophysical and geological studies intended to characterize the fault system in the locality of the drill site at various scales. In order to better understand the structural features of the central Alpine Fault, we have dev...

Among the outstanding tectonic questions regarding the convergence between the Tien Shan and Tarim basin in northwestern China are the manner in which deformation is accommodated within their lithospheres, and the extent that the Tarim lithosphere underthrusts the Tien Shan. In particular, the amount and type of deformation within the Tarim basin i...

The magmatic plumbing system beneath Askja, a volcano in the central Icelandic highlands, is imaged using local earthquake tomography. We use a catalog of more than 1300 earthquakes widely distributed in location and depth to invert for the $P$ wave velocity ($V_p$) and the $V_p$/$V_s$ ratio. Extensive synthetic tests show that the minimum size of...

We use seismic tomography to investigate the state of the supra-slab mantle beneath northern Chile, a part of the Nazca-South America plate boundary known for frequent megathrust earthquakes and active volcanism. We performed a joint inversion of arrival times from earthquake generated body waves and phase delay times from ambient noise generated s...

The magmatic plumbing system beneath Askja, a volcano in the central Icelandic highlands, is imaged using local earthquake tomography. We use a catalog of more than 1300 earthquakes widely distributed in location and depth to invert for the P-wave velocity (Vp) and the Vp/Vs ratio. Extensive synthetic tests show that the minimum size of any velocit...

We utilise seismic data from the central section of the Alpine Fault to locate earthquakes and image crustal structure in three dimensions. Tomography results from c. 6500 sources reveal the fault as either a southeast-dipping low-velocity zone or a marked velocity contrast in different parts of the study region. Where our model is best resolved, w...

The breakup of strong continental lithosphere requires more than far-field tectonic forces. Growing evidence for early-stage cratonic rift zones points to the importance of heat, magma and volatile transfer in driving lithospheric strength reduction. The relative contributions of these processes are fundamental to our understanding of continental r...

We investigate the fate of the Indian lithosphere following its descent beneath western Tibet by means of tomographic imaging based on arrival times of body waves from regional and teleseismic sources recorded by a portable network deployed in the region from 2007 to 2011. We use a non-linear iterative algorithm that simultaneously models absolute,...

With several rift segments at different stages of the rifting cycle, and the last orogenic episode more than 500 Mya, the young (<7 My) Eastern rift system in northern Tanzania and southern Kenya offers an ideal venue to study the role of magma and other fluids in continental rifting. To estimate both the location and volume of magma beneath the ri...

Rift initiation in thick, strong continental lithosphere challenges current models of continental lithospheric deformation, in part owing to gaps in our knowledge of strain patterns in the lower crust. New geophysical, geochemical, and structural data sets from youthful magmatic (Magadi-Natron, Kivu), weakly magmatic (Malawi, Manyara), and amagmati...

We studied the seismic velocity structure beneath the Krafla central volcano, NE Iceland, by performing 3D tomographic inversions of 1453 earthquakes recorded by a temporary local seismic network between 2009-2012. The seismicity is concentrated primarily around the Leirhnjúkur geothermal field near the center of the Krafla caldera. To obtain robus...

We present new, high-resolution, shear velocity models for the western Himalayas and West Tibet from the joint inversion of P receiver functions recorded using seismic stations from four arrays in this region and fundamental mode Rayleigh wave group velocity maps from 5–70 s covering Central and Southern Asia. The Tibetan Plateau is a key locality...

We describe a 2.5-D, frequency domain, viscoelastic waveform tomography algorithm for imaging with seismograms of teleseismic body and surface waves recorded by quasi-linear arrays. The equations of motion are discretized with p-adaptive finite elements that allow for geometric flexibility and accurate solutions as a function of wavelength. Artific...

The Tien Shan is the largest active intracontinental orogenic belt on Earth. To better understand the processes causing mountains to form at great distances from a plate boundary, we analyse passive source seismic data collected on 40 broad-band stations of the MANAS project (2005–2007) and 12 stations of the permanent KRNET seismic network to dete...

This is the version of record, which can also be found on the publisher's website at: http://gji.oxfordjournals.org/content/198/3/1526.full © The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society

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 northeastern margin of the Tibetan Plateau, which includes the Qiangtang and Songpan-Ganzi terranes as well as the Kunlun Shan and the Qaidam Basin, continues to deform in response to the ongoing India–Eurasia collision. To test competing hypotheses concerning the mechanisms for this deformation, we assembled a high-quality data set of approxim...

We study the elastic wave speed structure of the crust and the uppermost mantle in western Tibet using P and S-wave arrival times from regional earthquakes recorded by a temporary seismic network. We relocate the earthquakes, and subsequently invert travel time residuals for 3D distributions of wave speed. Resolution tests with a variety of input s...

We extend the 2.5D teleseismic full waveform inversion (FWI) algorithm of Roecker et al. (2010). The new algorithm inverts on a non-uniform mesh using the finite element method (FEM) to account for topographic effects, inputs teleseismic energy into the computational domain through a Bielak layer (Bielak et al., 2003), and improves the non-linear i...

The rifting cycle initiates with stress buildup, release as earthquakes and/or magma intrusions/eruptions, and visco-elastic rebound. Repeating cycles combine to produce the time-averaged rift zone architecture. Our aim is to quantify the time and length scales of faulting and magmatism in the cratonic East African rift system, which includes incip...

We use P wave and S wave arrivals from microseismic earthquakes to construct 3-D tomographic Vp and Vs images of the magma storage region beneath Askja's central volcano in the Northern Volcanic Zone of Iceland. A distinctive ellipsoidal low-velocity anomaly, with both Vp and Vsvelocities 8-12% below the background, is imaged at 6-11 km depth benea...

The geometry of the entire crust from the northern part of the Tarim Basin to the southwestern Tian Shan east of Kashi is imaged on a N-S-directed explosive-source deep seismic-reflection profile. The profile reflects the sedimentary formations in the northern part of the Tarim Basin and the fold-and-thrust belt of the southern Tian Shan. N-dipping...

The Tarim basin is distinct from the Tibetan plateau by the apparently low degree of internal deformation. Relative motion between the lithospheres of Tibet and Tarim likely results in coherent mantle deformation, with a diagnostic signature of anisotropic seismic wave speed. Birefringence (splitting) in core-refracted shear phases (SKS, PKS) obser...

Shallow-deep structure relationships for the junction belt is the import basis for the research and discussion of intracontinental orogenic dynamics. A deep seismic reflection profile of 121 km long, running in nearly SN direction, deployed in the junction zone between South Tianshan and Tarim basin to the east of Kashi, was completed in 2007. The...

Knowledge of the rock types and pressure-temperature conditions at crustal depths in an active orogeny is key to understanding the mechanism of mountain building and its associated modern deformation, erosion and earthquakes. Seismic-wave velocities by themselves generally do not have the sensitivity to discriminate one rock type from another or to...

Tomographic inversion with interstation Pn differential traveltime data provides a reliable velocity image of the uppermost mantle across the Longmenshan Fault Belt, which borders the eastern Tibetan plateau and Sichuan Basin. Low Pn velocities (<7.8 km/s) are revealed beneath the eastern Tibetan plateau to the west of the Longmenshan Fault Belt, w...

We present a method for imaging quasi-vertically dipping faults with surface records of reflected P waves from small earthquakes. Faults are boundaries between geological structures, such as tectonic plates, and are located in earthquake active regions such as Parkfield, California. The high degree of seismic activity enables the use of multiple se...

The convergence of the Philippine Sea and the Eurasian plates in the Taiwan region led to the formation of a young collisional mountain between two subduction zones of nearly orthogonal polarities. The geological processes underlying the collision and its relation to subduction are the primary targets of TAIGER (Taiwan Integrated Geodynamic Researc...

The 27 February 2010 Maule, Chile (Mw=8.8) earthquake is one of the best instrumentally observed subduction zone megathrust events. Here we present locations, magnitudes and cumulative equivalent moment of the first ˜2 months of aftershocks, recorded on a temporary network deployed within 2 weeks of the occurrence of the mainshock. Using automatica...

Numerous seismological experiments in central and southern Tibet have imaged the underthrusting Indian lithosphere and provided evidence of mid-crustal flow. A marked difference in mantle properties appears to occur in central Tibet, where body wave and Pn velocities become lower towards the north but with significant lateral variations. Surface wa...

We report a sequence of crustal quakes that began after the Mw = 8.8 thrust-subduction Maule earthquake that affected the Central Chile margin on 27 February 2010. This activity lasted by several months, having the most important events on 11 March 2010 (Mw = 6.9 and Mw = 7.0) with normal focal mechanisms. Seismicity shows a rupture oriented along...

The aftershock sequence of the Mw=8.8 Maule earthquake off the coast of Chile in February 2010 is one of the most well-recorded aftershock sequences from a great megathrust earthquake. Immediately following the Maule earthquake, teams of geophysicists from Chile, France, Germany, Great Britain and the United States coordinated resources to capture...

The Mw=8.8 Maule earthquake that occurred off the coast of Chile on February 27, 2010 is one of the largest megathrust earthquakes ever to be recorded and ruptured ~600 km of the plate boundary. This segment of the Nazca-South America plate boundary is an ideal region to investigate the processes related to the structure of the down-dip edge of the...

We adapt the 2.5D spectral domain finite difference waveform tomography algorithm of Roecker et al. (2010) to permit the analysis of teleseismically recorded surface waves. The teleseismic body wave technique of generating synthetic waveforms by specifying an analytic solution for a background wavefield in a 1D model and solving for a scattered fie...

The Geysers geothermal field is a source of significant small earthquake (M< 2.0) seismicity in northern California. The region has been actively monitored for seismicity, both natural and induced, since the geothermal field has been put into production. A modern digital seismic monitoring network in the area consists of 34 LBNL/Calpine (BG) boreho...

The TAIGER tomographic profiles across Taiwan present several robust features that are evidently related to the subduction-collision mountain building in Taiwan. In southern Taiwan, a steep, east-dipping high velocity anomaly in the 70-200 km range, associated with a Wadati-Benioff zone, can readily be recognized as a subduction zone; above the sub...

Reviewing data from regional permanent seismic stations and a 2001-2002 deployment of portable broadband seismic stations along the Tibet-Tarim border, we identified five unusually deep earthquakes located beneath the West Kunlun range. Application of regional centroid moment tensor analysis puts these events at depths of 40-60 km, with overall unc...

We apply the 2.5D full waveform tomographic imaging technique of Roecker et al. (2010) to data from the IRIS-PASSCAL Cascadia 1993 (CASC93) experiment conducted across central Oregon (Nabelek et al., 1993). Our main objective was to benchmark this imaging approach by comparing results with those previously determined Rondenay et al. (2001) using a...

Imaging the lithospheric structures under the Taiwan orogen is one of the key elements of the TAIGER project, aiming at resolving questions regarding the geodynamics of this young mountain range. Employing land as well as ocean bottom seismic stations (2700 total) and earthquakes (local and teleseismic) and explosions as sources we are able to deri...

The Mw=8.8 Maule earthquake off the coast of Chile on February 27, 2010 is the 5th largest megathrust earthquake ever to be recorded and the 2nd largest to be recorded by modern digital seismic networks. Immediately following the Maule earthquake, teams of seismologists from Germany, France, the UK, and the US, working with seismologists in Chile,...

We investigate the region of the ongoing collision between the India and Eurasia tectonic plates that results in widespread deformation of the continental lithosphere. Over the past decade, numerous regional studies were conducted between the Himalaya and the Tien Shan mountains, each illuminating a small part of the area. We combine the data from...

Distribution of the continental lithospheric strength is currently debated (e.g., ``jelly sandwich'' vs. ``crème brulee'' models). A key argument in this debate is the presence (or absence) of earthquakes in the lower crust and the upper mantle. The Tarim basin is commonly regarded as a relatively rigid block that lies between two actively deformed...

The Mw=8.8 Chilean megathrust earthquake of 27 February 2010 ruptured an interplate zone extending nearly 500 km along the coast of central Chile. Contrary to expectations, there has not been any major aftershock associated with the main rupture. Instead, the largest postseismic events thus far, a Mw=6.9 and a Mw=7.0 that occurred within 15 minutes...

Since the summer of 2007 we operate a network of 10 portable seismic stations in Western Tibet. To date we have recovered and archived data covering approximately 18 months, from July 2007 through March of 2009. Local seismicity of the region is poorly understood due poor station coverage in this remote part of China. The catalog compiled by the Ch...

The Tien-Shan mountains straddle the border between Kyrgyztan and northwestern China. The geodynamics of this orogeny is a subject of an ongoing debate (e.g., crustal shortening vs. subduction). Most of the recent investigations focused on the western part of the mountain range (west of 80 deg. E). That leaves the dynamics of the eastern part of th...

The abundant earthquake activity in the Chilean crust and upper mantle make Chile an outstanding environment for applications of seismological arrival time tomography. For the most part, applications of this type of imaging technique, which involves the joint determination of hypocenters and P- and S-wavespeed variations from the arrival times of p...

Beginning with the deployment of 15 PASSCAL instruments in June 2000, we have been developing increasingly refined models of the 3D crustal structure and more precise locations of the earthquakes around SAFOD. Our relocations of the target earthquakes (SF, LA, and Hawaii) guided the drilling trajectory for SAFOD, which passed successfully between t...

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1981. Supervised by Peter H. Molnar. Vita. Includes bibliographical references.

Recordings in western Tibet of Rayleigh and Love waves at periods less than 70 s from aftershocks of the 2008 Sichuan earthquake cannot be matched by an isotropic velocity model beneath Tibet. These intermediate-period Rayleigh and Love waves require marked radial anisotropy in the middle crust of Tibet, with the vertically polarized S-waves propag...

A global optimizing approach is developed and implemented to retrieve one-dimensional crustal structure by waveform inversion of teleseismic receiver functions. The global optimization for the inversion is performed using a Differential Evolution (DE) algorithm. This modeling approach allows the user to perturb, within a preset range of reasonable...

We have adapted a 2D spectral domain finite difference waveform tomography algorithm previously used in active source seismological imaging to the case of a plane wave propagating through a 2.5D viscoelastic medium in order to recover P and S wavespeed variations from body waves recorded at teleseismic distances. A transferable efficacy that permits...

We adapt a 2-D spectral domain finite difference waveform tomography algorithm previously used in active source seismological imaging to the case of a plane wave propagating through a 2.5-D viscoelastic medium in order to recover P and S wave speed variations from body waves recorded at teleseismic distances. A transferable efficacy that permits re...