Depth Of Discontinuity Research Articles

Seismic evidence for possible entrainment of rising plumes by subducting slab induced flow in three subduction zones surrounding the Caribbean Plate

The dynamic processes associated with subducting tectonic plates and rising plumes of hot material are typically treated separately in dynamical models and seismological studies. However, various types of observations and related models indicate these processes overlap spatially. Here we use precursors to PP and SS reflecting off mantle transition zone discontinuities to map deflections of these discontinuities near three subduction zones surrounding the Caribbean Plate: 1) Lesser Antilles, 2) Middle America and 3) northern South American subduction zones. In all three regions slow seismic anomalies are present behind the sinking slab within the transition zone in tomographic images. Using array methods, we identify precursors and verify their in-plane propagation for MW ≥ 5.8 events occurring between the years 2000 and 2020 by generating a large number of source receiver combinations with reflection points in the area, including crossing ray paths. The measured time lag between PP/SS arrivals and their corresponding precursors on robust stacks are used to measure the depth of the mantle transition zone discontinuities. In all three areas we find evidence for upward deflection of the 660 discontinuity behind the sinking slab, consistent with the presence of hot plume material (average temperature anomalies of 180 to 620 K), while there is not a corresponding downward deflection of the 410 km discontinuity. One interpretation of these disparate observations is suggested based on comparison to existing models of mantle convection and subduction: plume material rising across 660 km discontinuity could be entrained by lateral flow in the transition zone induced by the nearby sinking slab, and thus delaying the rise of hot material across the 410 km discontinuity.

Unveiling the Distinct Structure of the Upper Mantle Beneath the Canary and Madeira Hotspots, as Depicted by the 660, 410, and X Discontinuities

AbstractThe Canary and Madeira Islands are two distinct hotspots in the Central‐East Atlantic that are close to each other. Their volcanism is generally attributed to underlying mantle plumes, but the detailed structure of these plumes is still not well understood. The thermal and compositional structure of the plume introduces complexities in the phase transitions of the mantle, which impact the depth and magnitude of seismic discontinuities. We use 1,268 high‐quality receiver functions from stations located at the two hotspots to detect P‐to‐s converted phases through a common‐conversion point stacking approach and conduct a detailed analysis of mantle seismic discontinuities. The results show that both hotspots are characterized by a thin mantle transition zone (MTZ), with sharp 410 and 660 discontinuities at depths of 428–421 km and 647–664 km, beneath the Canaries and Madeira respectively. The results indicate that the Canary plume crosses the MTZ, whereas the Madeira plume mainly influences the upper portion of the MTZ. Furthermore, we find reliable detections of a sharp X discontinuity beneath the Canaries at 287 km. Its presence suggests the accumulation of silica‐rich recycled eclogite at these depths. We also use the amplitudes of P410s and PXs to derive velocity jumps at corresponding discontinuities. Based on these measurements, we estimate that the basalt proportion is 60%–80%, with accumulation being more significant in the Canaries than in Madeira. The MTZ thickness, the presence of the X discontinuity, and the high basalt proportion provide compelling evidence for a deep‐rooted thermochemical plume beneath the study area.

Depth of the lithospheric mantle discontinuities beneath the northwest flank of Oku Volcanic Complex, Cameroon Volcanic Line: constraints from mantle xenolith and teleseismic data

Depth of the lithospheric mantle discontinuities beneath the northwest flank of Oku Volcanic Complex, Cameroon Volcanic Line: constraints from mantle xenolith and teleseismic data

High-pressure single-crystal elasticity of corundum: Implication for multiple seismic structure of 660-km discontinuity

The complex multi-discontinuity structure at 660‐800 km depth is likely attributable to lateral mantle composition heterogeneities, which are closely related to the mid-ocean ridge basalts (MORB). To decipher the impact of varying composition on the seismic properties of MORB, detailed knowledge of the elasticity of candidate minerals is thus important. Here we employed Brillouin scattering coupled with diamond anvil cells to determine the single-crystal elasticity of corundum up to 14 GPa and 300 K. Using third-order finite strain equation of state, we calculate the pressure derivatives of adiabatic bulk modulus and shear modulus of corundum, which yields KS0’ = 3.8(1), G0’ = 1.8(1) with KS0 = 256(1) GPa and G0 = 163(1) GPa and ρ0 = 3.987(1) g/cm3. Combined with previous high-temperature data, the velocity and anisotropy of corundum have been calculated at 300 K or along normal geotherm. Our results are applied to model the density and velocity profiles of normal and alkali-depleted MORB. Our modeling demonstrates that varying the alkali content and temperature of MORB can significantly impact the discontinuity depth and velocity jump at 660–800 km depth. For normal MORB, reducing the temperature by 300 K from normal mantle geotherm results in a shift of the velocity jump from 670–710 to 650–710 km depth but hardly affects the magnitude of the velocity jump (5.8–6.8(3)% for VP and 10.0–10.8(5)% for VS). By contrast, in alkali-depleted MORB, the discontinuity will occur at a greater depth from 705–730 to 720–745 km depending on temperature with a VP jump of 3.8–4.6(2)% and VS jump of 6.3–7.4(4)%.

Moho Depth Estimation and The Presence of Subducting Slab in West Sumatra, Jambi, and Riau Islands Regions Using Teleseismic Receiver Function Method: A Preliminary Result

The teleseismic receiver function method was used to investigate the crustal structure in West Sumatra, Jambi, and Riau Islands regions. These regions have a high level of seismicity because it is in an active tectonic zone where the oblique subduction between the Indo-Australian and Eurasian plates occurs. This study aims to determine the depth of Moho discontinuity and the presence of subducting slab beneath 6 BMKG seismic stations that form a line perpendicular to the trench and cover 3 different geological zones. PPSI and RASM are in the forearc zone, SKSM is in the volcanic arc zone, and MBBI, JMBI, and DSRI are in the back-arc zone. This study used teleseismic earthquake record data with epicentral distance between 30°-90° from the receiver and magnitude 6 or more. The iterative time-domain deconvolution and receiver function migration techniques were applied to estimate the depth of Moho discontinuity and the presence of subducting slab. The depth of Moho discontinuity in West Sumatra, Jambi, and Riau Islands regions ranges from 21-39 km and generally deeper in the volcanic arc zone possibly due to the isostatic effect. Moho is at a depth of 21-29 km in the forearc zone, 36-39 km in the volcanic arc zone, and 30-36 km in the back-arc zone. Then the subducting slab was observed at a depth of 20 km under PPSI station to 200 km under MBBI station.

Identification of Moho Discontinuity Depth and Subduction Slab in Bengkulu and South Sumatra Region using Receiver Function Method: A Preliminary Result

Bengkulu and South Sumatra regions are areas with high seismic activity due to faults and subduction zones. This study aims to analyze the depth of the Moho discontinuity layer and subduction slab under 4 BMKG seismic stations that form a perpendicular line of trench in the Bengkulu and South Sumatra areas. The distribution of stations used are Enggano Station (EGSI) in the front arc islands, Manna Station (MNAI) in the front arc basin, Pagar Alam Station (PKSI) in the volcanic-arc zone, and Lahat Station (LHSI) in the proto-volcanic zone. We selected teleseismic earthquake data with a distance of 30°-90° from the stations and magnitudes above 6 (M>6). For the identification of Moho and slab depths, we used analysis of receiver functions with iterative time domain deconvolution and migration of receiver functions with the AK-135 velocity model. The Oceanic Moho layer and the subduction slab under the EGSI Station were identified at depths of 34 km and 23 km respectively, under the MNAI Station the Moho layer and the subduction slab were identified at a depth of 18 km and 87 km respectively, under the PKSI Station the Moho layer and the subduction slab were identified at a depth of 34 km and 129 km respectively, and under the LHSI Station the Moho layer and subduction slab were identified at depths of 35 km and 175 km respectively.

Preliminary Results on Receiver Function Study in Mt Merapi, Central Java, Indonesia

Mount Merapi, a stratovolcano, is the world’s most active volcano, with a relatively short eruption period. Mount Merapi formed in the Java region as a result of regional tectonics dominated by the Sunda Arc, resulting in a large earthquake. Many earth scientists are interested in studying the volcano’s subsurface conditions due to its relatively short eruption period and interesting geological features. The Receiver Function method was used in this study to determine the crust’s depth and assess the presence of a LVZ (low velocity zone) by reprocessing receiver function data. The Receiver function is used to identify the Moho discontinuity area by converting P to S waves. A total of 100 earthquake data from 8 teleseismic stations were successfully downloaded from the IRIS website, that was distributed into sections A-A′ (west side of Mount Merapi) and B-B’ (east side of Mount Merapi). The processing of the receiver function data, as shown by the stacking align results, shows that the closest teleseismic station at west side of Mount Merapi has a very strong negative amplitude response, which is represented as a LVZ or magma reservoir after the arrival of P wave. To estimate the zone for LVZ, a forward modeling receiver function technique was used to find the best correlation between the Synthetic Receiver Function curve and the Receiver Function observation curve. A forward modeling receiver function technique was used to find the best correlation between the Synthetic RFcurve and the RF observation curve to estimate the zone for the LVZ. The correlation between the synthetic RF curve from Ramdhan et al’s (2019) tomographic velocity model and the observed RF curve is poor. To improve the correlation, include the main signal source that affects the receiver function curve in the form of seismic wave velocity particularly Vs, LVZ Zone, thin sedimen layer or shallow reservoir, and depth of discontinuity by Suhardja et al (2019). The estimated depth of the LVZ at 10 - 17 km is thinning towards the south or towards Mount Merapi, according to the results of the synthetic receiver function curve modelling at the closest station to Mount Merapi.

On the Importance of Using Directional Information in the Search for Lower Mantle Reflectors

Abstract The SS precursor signals are a powerful tool for mapping topography of mantle discontinuities, which are sensitive to the thermal and compositional structure of the mantle. The depth of mantle discontinuities is usually estimated using the differential travel time between the main arrival and its precursor. However, this method ignores potential travel path deviations that influence the travel time of precursor signals. Here, we use an approach that considers directivity information as well as travel-time measurements. Applying seismic array techniques, we measure slowness, back azimuth, and travel time of the signals, and use this information to backproject to the point of reflection. In our test dataset, we observe deviations from the predicted values in slowness and back azimuth in the range of 0.1–2.3 s/° and 1–20°, respectively. These values lead to reflection locations that can differ considerably from theoretical reflection points calculated with great circle plane paths as well as depths different from the depth calculated for in-plane propagation, with differences up to ∼150 km. Our results indicate that the travel-path deviations should be considered to avoid misinterpretation of mantle discontinuities and potentially reduce previously observed scatter in discontinuity depth.

Heat flow modelling of the Punta del Este Basin (offshore Uruguay) and its correlation with structural crustal domains

The Punta del Este Basin is located at the offshore of Uruguay, and it is considered an underexplored basin with a high potential for holding hydrocarbon plays. Geologically, it constitutes an aborted rift related to the Gondwana fragmentation process, and subsequent opening of the Atlantic Ocean (Upper Jurassic - Lower Cretaceous). The stratigraphic and tectonic evolution comprises four phases from the Paleozoic pre-rift stage to present-day post-rift stage (Neogene/Quaternary). Due to the estimated hydrocarbon potential of this basin, exploratory activities have been intensified in the last decades, based on the acquisition of a significant amount of geophysical data which allowed a better comprehension of the basin's geology. Previous studies related to this basin were mainly oriented to the stratigraphy, structural framework, and petroleum systems comprehension. This research is focused on the thermal evolution of the Punta del Este Basin and its correlation with the crustal geological structure. For this purpose, a heat flow model was developed in order to understand thermal evolution through geological time. A 2D heat flow modelling based on pseudo wells was carried out to research and reconstruct the paleo heat flow. Bottom-hole temperatures (BHTs), seabed heat flow measurements, and Moho discontinuity depth interpretations have been employed in the reconstruction of heat flow evolution through time. A structural analysis based on seismic interpretation allowed to identify the Moho discontinuity and define four crustal domains in the study area: proximal (unattenuated crust), necking, hyperextended (stretched and thinned transition crust), and oceanic crust. The thermal model shows a strong correlation between heat flow and crustal thickness. In this way, the proximal domain develops low heat flow values while the distal sector shows higher values, due to the strong influence of the rifting event in crust thinning.

The topography of the 660-km discontinuity beneath the Kuril-Kamchatka: Implication for morphology and dynamics of the northwestern Pacific slab

The 660-km discontinuity (660) plays a potentially important role in deep slab dynamics and mantle convection. Increasing numbers of seismic observations suggest controversial morphologies of the Pacific slab beneath the Kuril-Kamchatka, highlighting the poorly understood interaction of the slab and mantle discontinuities. Here we collect near-source S-to-P converted waves from a large dataset with several dense seismic networks and systematically image the topography of the 660 around the Pacific slab beneath the Kuril-Kamchatka. We conduct detailed comparisons of the 660 depths and seismicity along some vertical cross sections. In comparison with the discontinuity depth in the IASP91 model, the 660 exhibits broad depressions up to 32–63 km with apparent downward deflections beneath the Kamchatka Peninsula and northern Kuril (region I), supporting slab penetration into the lower mantle; in contrast, the 660 depressions beneath southern Kuril (region II) are less than 21–28 km with a relatively flat configuration, implying a stagnating slab with possible hot entrained mantle materials and/or partial melts below it. We interpret these regional variations in the 660 topography as reflecting local low-temperature anomalies due to different slab morphologies associated with contrasting subduction modes. We suggest compound effects of pressure-driven mantle flow and trench retreat for inducing the inferred subduction mode change of the Pacific slab from region I to region II. Our results can provide more insight into subduction dynamics in the northwestern Pacific.

Nature of mantle discontinuities beneath the Ontong Java Plateau

We determined the depths of the mantle discontinuities with a receiver function method using broadband data recorded on the seafloor and islands of the Ontong Java Plateau (OJP) and its vicinity. The 410-km discontinuity is broadly elevated by 10–20 km beneath the OJP. The elevation is observed in the low-velocity region above a stagnant paleo-Pacific slab that had been subducted until 25 Ma. The elevated 410-km discontinuity and the slow anomalies may be caused by partial melting induced by hydration with water released from the paleo-Pacific slab. The 660-km discontinuity is close to the global average beneath the OJP, suggesting that the stagnant Pacific slab is bottoming in the mantle transition zone. The 410-km discontinuity is depressed by 10–20 km beneath the Caroline volcanic chain, where a low-velocity sheet has been observed by tomographic studies, implying that a sheet-like upwelling occurs at least from the top of the mantle transition zone. The 660-km discontinuity is also depressed by 10–30 km beneath the Caroline volcanic chain, which may be attributed to the majorite-bridgmanite phase change in a high-temperature environment and/or an underestimated velocity correction in the moveout correction of receiver functions. It is thus unclear whether the sheet-like mantle upwelling has its roots in the lower mantle.

A new approach to construct 3-D crustal shear-wave velocity models: method description and application to the Central Alps

We develop a new inversion approach to construct a 3-D structural and shear-wave velocity model of the crust based on teleseismic P-to-S converted waves. The proposed approach does not require local earthquakes such as body wave tomography, nor a large aperture seismic network such as ambient noise tomography, but a three-component station network with spacing similar to the expected crustal thickness. The main features of the new method are: (1) a novel model parametrization with 3-D mesh nodes that are fixed in the horizontal directions but can flexibly vary vertically; (2) the implementation of both sharp velocity changes across discontinuities and smooth gradients; (3) an accurate ray propagator that respects Snell’s law in 3-D at any interface geometry. Model parameters are inverted using a stochastic method composed of simulated annealing followed by a pattern search algorithm. The first application is carried out over the Central Alps, where long-standing permanent and the temporary AlpArray Seismic Network stations provide an ideal coverage. For this study we invert 4 independent parameters, which are the Moho discontinuity depth, the Conrad discontinuity depth, the P-velocity change at the Conrad and the average Vp/Vs of the crust. The 3-D inversion results clearly image the roots of the Alpine orogen, including the Ivrea Geophysical Body. The lower crust's thickness appears fairly constant. Average crustal Vp/Vs ratios are relatively higher beneath the orogen, and a low-Vp/Vs area in the northern foreland seems to correlate with lower crustal earthquakes, which can be related to mechanical differences in rock properties, probably inherited. Our results are in agreement with those found by 3-D ambient noise tomography, though our method inherently performs better at localizing discontinuities. Future developments of this technique can incorporate joint inversions, as well as more efficient parameter space exploration.

Petrology of the magmatic system beneath Osorno volcano (Central Southern Volcanic Zone, Chile)

Petrological studies of volcanic systems and magmatic processes provide small-scale information that are inaccessible to the current resolution of geophysical tools. In the Southern Volcanic Zone of the Chilean arc, Osorno ranks sixth in the official risk classification in a region of increasing vulnerability due to soaring human activities coupled with lahar hazard and the threat of a tsunami induced by a flank collapse. However, its magmatic system remained poorly investigated. Here, we present and integrate to existing geophysical models a comprehensive set of petrographic and geochemical data including whole-rock and mineral major and trace element analyses, associated with detailed numerical modelling to constrain the storage conditions below Osorno. To capture the full complexity of the system, over 154 samples of all known major units of the volcano have been collected. They cover a large range from tholeiitic primary basalt (Mg# = 0.72 and ≥ 50 wt% SiO 2 ) to rhyodacite (Mg# = 0.18 and ≥ 70 wt% SiO2), displaying a compositional gap within andesite (59–63 wt% SiO 2 ). This gap results either from andesitic melt thermal instability or from the interstitial melt extraction of the crystal mush. Basalt and basaltic andesite lava with plagioclase and olivine (± clinopyroxene) are dominant. Their crystallinity largely varies from 1 to 53 area % with the lowest values in the most evolved basaltic andesites. Dacites are limited to three small domes with low crystallinities between 7 and 13 area %. The presence of diktytaxitic enclaves within the dacites indicate minor mingling with a less differentiated melt. Water-bearing phases are generally absent, except for one dacite sample where few small amphibole crystals occur. Petrology, chemical data and thermobarometric results imply shallow fractional crystallization of troctolitic, gabbroic and gabbronoritic cumulates. Differentiation dominantly takes place between 2 and 3 kbar (6–10 km) and results from a water-poor (≈1 wt% H 2 O), tholeiitic parental melt. No evidence of high-pressure fractionation was observed. We interpret this differentiation depth as Osorno's main storage zone. It correlates with the depth of the intracrustal discontinuity and seismic reports below the volcano. Only the upper half of the storage zone, imaged with geophysical methods, was erupting. We suggest a comparable behavior for a potential future event. • Basalt evolves to dacite at ≈2 kbar near the depth of the intracrustal discontinuity. • Fractional crystallization dominates under water undersaturated conditions. • Petrographic observations and numerical models were integrated with geophysical data.

High-resolution transdimensional geoacoustic inversion using autonomous underwater vehicle data

We invert reflection coefficient measurements of muddy sediment layers along a 12-km seabed transect on the Malta Plateau in the Mediterranean Sea using 1711 source transmissions recorded on a 32-element linear hydrophone array with both source and array towed by an autonomous underwater vehicle. Trans-dimensional Bayesian inference using reversible jump Markov chain Monte Carlo sampling is applied to obtain posterior probability densities of the number of homogeneous sediment layers, their depths, and their geoacoustic parameters. The forward sediment acoustics model is based on the grain-shearing model which obeys physical causality and provides correlation between important geoacoustic properties. Each dataset was treated as one-dimensional seabed structure inversion carried out on high performance clusters, and inversion results for multiple data sets were combined to yield a two-dimensional subsurface profile including full uncertainty analysis. Comparisons of inversion results to piston and gravity core estimates show agreement in both geoacoustic parameter values and depths of discontinuities. In the range-dependent model constructed from inverting the entire data set, dipping and terminating layers are observed along the track with high vertical resolution on the order of 10 cm.

Predicting and Scoring Estuary Ecological Health Using a Bayesian Belief Network

Excessive nutrient and sediment inputs threaten ecological condition in many estuaries. We describe a Bayesian Belief Network (BBN) that calculates an Estuary Trophic Index (ETI) score ranging between 0 (no symptoms of eutrophication) to 1 (grossly eutrophic) for estuaries in Aotearoa New Zealand (NZ). The ETI BBN includes estuary physiographic characteristics (estuary type, flushing time, intertidal area, estuary closure state, water column stratification) and nutrient and sediment loads available from existing geospatial tools and databases, that drive responses of ‘primary’ indicators (macroalgae and phytoplankton biomass) and ‘secondary’ indicators (or symptoms) of estuary ecological impairment (sediment carbon, sediment apparent redox potential discontinuity depth, water column oxygen, macrobenthos and seagrass condition). Relationships between the BBN nodes are based primarily on observational and model-based information from NZ and international studies rather than expert opinion. The model can be used in a purely predictive manner under knowledge-poor situations, using only the physiographic drivers and nutrient/sediment loads, or refined using field-derived observations of indicator values to reduce the uncertainty associated with the probabilistic BBN score. It is designed for shallow tidal lagoons, tidal river estuaries and coastal lakes; systems which are sensitive to eutrophication and sedimentation pressure and are common in NZ and globally. Modelled ETI BBN scores agreed well with ETI scores calculated from observed indicator values for 11 well-studied NZ estuaries. We predict ecological condition of 291 NZ estuaries, most of which have no monitored information on trophic state. We illustrate capabilities of the ETI BBN with two case studies: to evaluate improvements in estuary health arising from diversion of wastewater from an estuary via an ocean outfall, and to estimate catchment diffuse nutrient load reductions required to meet estuary health objectives. The ETI BBN may serve as a template for other agencies wishing to develop similar tools.

Crustal structures beneath the Northern Jiangsu Basin and its surrounding areas: implications for geothermal prospecting

Abstract Based on the recordings of 42 permanent seismic stations in Northern Jiangsu Basin (NJB) and its surrounding areas, we obtained both the sediment and crustal thickness in the region, using the nearest-neighbor algorithm and H–κ stacking method of receiver functions. We proposed a solution to use the sediment thickness to correct the depth of actual Moho discontinuity beneath the basin areas. Our results indicate that the sediment thickness in the northwest of the NJB is <1 km. We suggest that the southeastern border of the NJB should extend to the Yangzhou-Rudong area. The results of Moho variations show that the undulations of the Moho beneath the western NJB retains the traces of the sinistral shearing movement of the Tan-Lu Fault since the Miocene. Finally, we suggest the area around the Gaoyou city to be a prospective area for geothermal exploration.

National depth and R&D alliance portfolio international expansion: The moderation of technological discontinuity and long-term orientation

Numerous studies have reported the positive outcomes of an expanded international R&D alliance portfolio, yet very few investigate what drives its international expansion. This study fills the gap by developing a three-dimensional frame that demonstrates the national depth of prior alliance portfolio (ND), technological discontinuity (TD), and long-term orientation (LTO) to understand antecedents further. First, this study examines the role of ND by illustrating its trust mechanism derived from transaction cost economies and the learning mechanism based on organizational learning theory. Second, it investigates TD'S moderation role by explaining how it mitigates trust and learning mechanisms of ND from the resource-based view. Third, it explores LTO's three-way moderation role by elaborating on how it impacts decision-making. It develops novel quantitative measures and conducts empirical analysis using multi-source matching data of 106 firms spanning 11 years (2006−2016). Results show that national depth negatively impacts R&D alliance portfolio international expansion. High technological discontinuity weakens the negative impacting strength of national depth. High long-term orientation weakens the moderation strength of technological discontinuity.

Ground motion characteristics and the depth of the S-wave velocity discontinuity in the post-LGM incised-valley fills beneath the Tokyo Bay area, central Japan, based on microtremor surveys

Ground motion characteristics and the depth of the S-wave velocity discontinuity in the post-LGM incised-valley fills beneath the Tokyo Bay area, central Japan, based on microtremor surveys

Comparison Study of Crustal Structure in Aceh Region based on Volcanic Arc System using Receiver Function Method

Aceh region has a very complex crustal structure from the forearc ridge to the backarc basin. This study aims to determine the velocity model of P and S waves and the depth of Moho discontinuity. This research was conducted using teleseismic earthquake data (30°-90° from the station) with M>6 from four seismic stations belonging to the BMKG in Aceh region. The stations are qualified based on the volcanic arc system zone. Furthermore, the velocity model determined by result of forward modelling, while the depth of the Moho layer estimated by migrated receiver function from time domain to the depth domain. At station SNSI that represented the forearc ridge zone, the depth of Moho is ±28 km, at station TPTI represent the forearc basin is ±16 km, while at zone with higher topography, namely volcanic arc zone represented by station KCSI, the Moho depth was identified at ±38 km, and the backarc basin represented by station LASI with ±40 km depth of Moho. This variation occurs because the composition of the earth’s layers below the station is diverse also different topography for each station.

Constraining the 410-km discontinuity and slab structure in the Kuril subduction zone with triplication waveforms

SUMMARYThe detailed structure near the 410-km discontinuity provides key constraints of the dynamic interactions between the upper mantle and the lower mantle through the mantle transition zone (MTZ) via mass and heat exchange. Meanwhile, the temperature of the subducting slab, which can be derived from its fast wave speed perturbation, is critical for understanding the mantle dynamics in subduction zones where the slab enters the MTZ. Multipathing, i.e. triplicated, body waves that bottom near the MTZ carry rich information of the 410-km discontinuity structure and can be used to constrain the discontinuity depth and radial variations of wave speeds across it. In this study, we systematically analysed the trade-off between model parameters in triplication studies using synthetic examples. Specifically, we illustrated the necessity of using array-normalized amplitude. Two 1-D depth profiles of the wave speed below the Tatar Strait of Russia in the Kuril subduction zone are obtained. We have observed triplications due to both the 410-km discontinuity and the slab upper surface. And, seismic structures for these two interfaces are simultaneously inverted. Our derived 410-km discontinuity depths for the northern and southern regions are at 420$\pm $15 and 425$\pm $15 km, respectively, with no observable uplift. The slab upper surface is inverted to be located about 50–70 km below the 410-km discontinuity. This location is between the depths of the 1 and 2 per cent P-wave speed perturbation contours of a regional 3-D full-waveform inversion (FWI) model, but we found twice the wave speed perturbation amplitude. A wave speed increase of 3.9–4.6 per cent within the slab, compared to 2.0–2.4 per cent from the 3-D FWI model, is necessary to fit the waveforms with the shortest period of 2 s, indicating that high-frequency waves are required to accurately resolve the detailed structures near the MTZ.