Analysis of crustal deformation is key to understand current tectonics, deformation processes and seismicity. However, there is no consensus to date on how to integrate geodetic strain rates in seismic hazard models for continental intraplate regions. Most of Western Europe and mainland France are located within the Eurasia Plate, with very low deformation and seismicity rates, and GNSS velocities that comprise different sources, from tectonic contributions (e.g., fault motions) to non-tectonic long-term or transient processes (e.g., Glacial Isostatic Adjustment - GIA). Some of these processes also reflect stress changes at depth, loading of active faults, and seismicity. Understanding this deformation is therefore key to better assess seismic hazard in slow straining areas. In order (i) to assess the variability due to the diversity of strain-rate calculation methods and (ii) to test their capacity to resolve low-amplitude deformation, we conduct a benchmark exercise based on synthetic velocity fields comprising background noise (with the same characteristics as that observed in mainland France) plus velocity signals from various geodynamic processes. Comparing to the expected values the strain rates derived independently by eight different methods, four main conclusions can be drawn. (1) The capacity to deal with velocity noise and recover large-scale or local signals vary strongly between the methods, with some standing out from the others. (2) No method is able to retrieve the strain rate signals associated with active faults slipping at rates of 0.3-1 mm/yr (i.e. larger than expected for mainland France). (3) No method is able to retrieve the small deformation associated with a potential hot spot under the Massif Central (similar to, but about twice lower than observed for the Eifel hotspot). (4) Some methods are able to retrieve parts of the large-scale strain rate patterns (but not the amplitudes in general) associated with Alpine GIA or rotating rigid blocks. These results must be interpreted with caution, keeping in mind the strict benchmark design. They point out the potential for improvements in future analyses of geodetic deformation in mainland France and continental intraplate context in general.

The South Peru subduction zone is a complex, highly active region, where the flat slab associated with the Nazca Ridge subduction in the North transitions to a much steeper subduction in the South. This transition not only causes the slab to contort, but affects seismicity patterns in the region. Here we use data from 26 seismic stations active from March 2022 to December 2024 as part of the DEEPTrigger project, along with 16 permanent Peruvian stations and 15 permanent Chilean stations, to create a 3-year seismicity catalogue of South Peru. Using PhaseNet for phase picking and PyOcto for phase association, we obtain a total of 166 971 events. These earthquakes are located with NonLinLoc-SSST using a new 3-D P and S-wave velocity model of the region obtained from full-waveform inversion (Kan et al., 2025), then relocated using double difference methods with cross-correlation times to obtain precise locations. We thus obtain the first dense and precisely-located earthquake catalog of the region.With this new catalog, we are able to demonstrate the influence of the Nazca Ridge on seismicity patterns. We find numerous shallow seismic swarms where the ridge enters subduction, while they are absent from the rest of the margin. In combination with GPS records of nearby stations, they hint at the likely presence of slow slip. We also find that the edge of the Nazca Ridge is particularly active, down to depths below 80 km. This same edge was activated by the Mw 7.2 Acari earthquake which occurred on June 28th 2024 at the plate interface, and was preceded by a Mw 6.0 intraslab foreshock on June 16th 2024. The Acari mainshock triggered a large aftershock expansion towards the northwest where the Nazca Ridge subducts, and a triggered swarm and possible SSE in that region. It also caused an increase of intraplate seismicity directly downdip along the Nazca Ridge edge, demonstrating the ridge’s ability to concentrate stress.

Understanding the mechanisms controlling deformation localization is crucial for our understanding of fault mechanics and improving seismic hazard assessment, but has not been extensively studied for normal-faulting earthquakes. Here, we present a thorough analysis of the 2016 Mw 6.5 Norcia, Italy, earthquake using high-resolution satellite geodesy. We investigate the degree of deformation localization, evaluate its controlling factors and the link with the distribution of slip with depth. Using the optical image correlation technique with an innovative method for noise correction, we measure the near-field 3D displacements associated with the Norcia event. Based on these measurements, we quantify the amount of off-fault deformation (OFD) and evaluate how it varies with external factors. We find 46% (25 cm) of OFD on average and a strong correlation with local topographic slope and near-surface lithology, with increased distributed deformation where ruptures traverse unconsolidated sediments and areas of gentler slopes. In contrast, the correlation between OFD and the fault segment orientation relative to the regional stress field is weak. We develop a comprehensive slip model accounting for complex multi-segmented fault geometry, topography, and 3D elastic structure through a joint inversion of optical, InSAR, and GPS data. The inversion reveals a highly heterogeneous slip distribution characterized by large slip (up to 3.5 m) at depth, and several shallow slip patches. We find a pronounced average shallow slip deficit (SSD) of 72%, with no along-strike correlation between SSD and OFD. This suggests that the OFD primarily reflects surficial inelastic processes occurring within the shallow soil.

Viscoelastic relaxation following large subduction earthquakes is known to last from years to decades, and affect the interseismic loading rate up to hundreds of kilometers in the trench perpendicular direction. Post seismic relaxation also generates a rotation pattern close to the edges of the ruptured asperity. Recently, several observations reported an accelerated loading rate coeval with megathrust ruptures, at along-trench distances from the epicenter of hundreds of kilometers.Proposed models involved so far viscoelastic relaxation in the mantle wedge and the oceanic mantle, as well as a weak oceanic LAB layer. However those models often fail to explain simultaneously the amplitude and the spatio-temporal patterns of the observations.Here, we perform 3D viscoelastic models of post seismic relaxation and explore a range of structural and rheological settings to investigate the mechanisms responsible for the complex loading variations observed. The tested scenarios include a Burgers rheology, viscosity contrasts between the continental and oceanic mantles, a weak LAB, and a low-viscosity layer overlying the subducting slab.The relevance of these different models is evaluated by comparing their predictions with geodetic observations following several large earthquakes along the Chile–Peru subduction zone, allowing us to assess to assess the relative importance of the proposed mechanisms.

Kinematic coupling models inverted from geodetic data are widely used to evaluate how slip deficit is distributed along subduction megathrusts during the interseismic period, and are central to earthquake and tsunami hazard assessment. Yet, existing coupling models differ widely in methodology and inputs, lack common community standards, and are scattered across publications and repositories. Here, we introduce the "Coupling Cloud" (https://couplingcloud.ucsd.edu), an open, extensible, community-driven platform that curates, standardizes, documents, and disseminates more than 96 kinematic coupling models from 55 publications across 21 subduction margins. The platform provides interactive 2D and 3D plate-interface viewers to inspect coupling models together with associated information such as slab geometry, uncertainty estimates and metadata. All datasets can be downloaded directly in standardized formats: surface-projected coupling values as NetCDF, plate-interface dislocation geometries as VTU, and model metadata as YAML files. We demonstrate the advantages of centralized and standardized coupling data through a Cascadia subduction zone example, where synthesizing eight full-margin models reveals along-strike patterns that are not apparent when models are examined individually. Consolidating coupling models within a coherent, version-controlled framework enables systematic cross-margin comparison and FAIR-compliant data sharing, opening the door to more comprehensive assessment of megathrust mechanics.

Accurate P-wave polarity picking is crucial for determining focal mechanisms, yet difficult to automate, especially for smaller magnitude events (typically M < 4) with their low signal-to-noise ratio. Recently, deep learning models have shown promising performance for automatic polarity determination. However, as training data is limited to the long-term manual picks, performance on new regions and different tectonic settings is often unclear. This calls for models with strong cross-regional generalization, robustness to method-dependent picking errors and data-quality variations, and overall stable performance across diverse seismic network. Here, we train a deep-learning CNN-based model similar to the one proposed by Ross et al. (2018) previously demonstrated to be highly effective for a massive P-polarity picking. To avoid biases from dataset imbalance, we train the network explicitly to adhere to physical symmetry properties of seismic data. We systematically verified the model's transferability to different regions and tectonic settings using six hand-curated datasets representing diverse margin, intraplate and induced seismicity with various depths, distances and magnitude ranges. Our model is trained to remain robust under P-wave arrival time uncertainties of up to 1s. We make the most performant model, trained on more than 3 million examples from diverse regions, available for community use through SeisBench.

The subduction megathrust and its frictional properties are central to controlling the short- and long-term dynamics of subduction zones. While the frictional properties are largely controlled by the 3D structure of the megathrust interface, our understanding of this structure is limited. Exhumed outcrops provide evidence for a complex mélange of ductile and brittle materials, which is segmented in a fractal manner. However, for active subduction zones, we lack direct evidence for such fine-scale structural segmentation as well as quantitative constraints on the segmentation structure.Here, we use two high-resolution earthquake catalogs from the South American subduction margin to characterize the fine-scale segmentation in situ. We show that two overlying processes govern the fractal distribution of earthquake hypocenters. At short time scales, aftershock clustering dominates the earthquake distribution. At long time scales, averaging over many mainshock-aftershock sequences, the underlying structure shows. However, with typical catalog durations of only a few years, it is crucial to infer structure from short-term catalogs as well. We show, both theoretically and in our observational data, that even in short-term catalogs, structural constraints can be derived by looking at near-field interactions (< 100 m).Based on our analysis, we find a fractal segmentation of the subduction interface in Northern Chile and Southern Peru with a fractal dimension D=1.6-1.7. This is consistent with the fractal distribution of brittle inclusions in exhumed outcrops. Notably, the fractal distribution is stable down to the hypocenter uncertainty (< 10 m), suggesting self-similarlity over several orders of length. We find an increase in fractal dimension with depth, suggesting a more uniform interface in the downdip region. This work provides a method to gain direct insights into the structure of the subduction interface and systematically quantify it. This way, we aim to connect structural observations to frictional properties and large scale dynamics.

The fluid cycle in subduction zones prescribes large parts of its structure and seismogenic behavior. Background seismicity inside the downgoing slab is linked to fluid release from dehydration reactions, whereas fluid overpressure along the plate interface can alter interplate coupling, megathrust earthquakes, and the presence or absence of slow-slip events (SSEs) and tectonic tremor. We present a high-resolution seismic tomography model of the Atacama segment in northern Chile, the only region along the Chilean margin where SSEs have been observed. Using traveltimes from over 8,800 seismic events determined using state-of-the-art algorithms (EQTransformer, PyOcto), we followed a staggered workflow (VELEST, SIMUL2023) to derive consistent 1D, 2D and 3D models of P-wave velocity and ratios, achieving high spatial resolution in the upper continental crust, mantle, and downgoing slab. The final 3D model reveals key features interpreted as subsurface fluid processes. High (1.80) appears along the plate interface, with localized anomalies in the mantle wedge and lower continental crust. Regions with deep seismicity (similar to 80-100 km depth), notably around the Copiap & oacute; Ridge, exhibit zones of higher ratios (1.82) extending upward from the oceanic slab into the continental crust, which otherwise shows lower ratios (1.76). These observations reflect along-strike variations in dehydration-driven fluid release accompanied by microseismicity. Liberated fluids ascend into the mantle wedge and updip along the slab surface, where they may influence SSEs. Our results provide new constraints on possible fluid pathways and crustal heterogeneity, highlighting the role of fluids in modulating seismogenic processes.

Slow, aseismic fault slip has emerged as a significant contributor to the seismic cycle. However, whether slow and fast slip arise from similar physical processes remains unresolved, due to detection biases affecting noisy surface measurements and the analysis of the source properties of slow slip. Using daily geodetic time series denoised with a deep learning model, we invert for 15 years of slow slip evolution on the Cascadia subduction with unprecedented temporal resolution. Our observations show that an upper bound for slow-slip moment rates exists, and that scaling laws are strongly influenced by the chosen detection threshold and the signal-to-noise ratio. Moment rate functions evolve with magnitude: slow slip nucleates as a two-dimensional expanding crack, propagating laterally when encountering the along-dip limits of the transition zone. Our findings highlight a continuum of slow slip events of various sizes controlled by subduction interface geometrical constraints.

The South Peru subduction zone is a complex, highly active region, which has hosted four Mw 8+ earthquakes over the last 100 yr. It marks the transition between the flat slab associated with the Nazca Ridge subduction in the North and more steeply dipping subduction in the South, causing the slab to contort and affecting seismicity patterns in the region. In this study, we present the first high-density, high-quality seismic catalogue of the region between the arc and the trench, totalling 166 825 events between 2022 January 1 and 2024 December 31, including 125 467 well-located ones. We first picked and associated phases using PhaseNet and PyOcto, then located the resulting events with NonLinLoc-SSST and GrowClust3D. Finally, we derived a new slab model from the seismicity, allowing us to classify the earthquakes as upper plate (16 per cent), interface (12 per cent), lower plate (68 per cent), outer rise (0.20 per cent) and human-related (3.1 per cent). The region is broadly divided into four subregions with different seismicity patterns and slab geometries: the flat slab, with intense interface and intraslab activity, the slab transition zone, where the plate contorts to accommodate its change in geometry, the Arequipa region, with intense upper plate seismicity but very low intraslab and interface seismicity and the North Chile region, with a large band of dense intraslab seismicity. We find that in the flat slab region, the Nazca Ridge is linked to the presence of dense seismicity close to the trench, and seismic swarms hinting at the presence of slow slip. Meanwhile, the intraslab seismicity in that region is organized in trench-parallel bands which are likely related to slab bending. In the slab transition region, we image multiple orthogonal faults just south of the slab contortion, suggesting a damaged slab. Further south, in the Arequipa region, upper plate seismicity forms a large, trenchward-dipping structure seemingly connected to the Incapuquio fault at the surface. Finally, in North Chile, the deep band of intraslab seismicity appears to locate further downdip as we move to the north, perhaps reflecting changes in slab properties.

The mantle wedge seismicity of the Atacama segment of the Northern Chilean subduction, a region with complex slab geometry, has recently been mapped in a high-density seismicity catalog. In order to better constrain the underlying mechanisms responsible for its occurrence, we investigate the spatio-temporal evolution of the seismicity along the plate interface and within the overriding (upper) plate. We find that the b-value of the mantle wedge seismicity is consistently greater than 1, averaging around 1.5, and that for earthquakes of similar magnitude, there are few, if any, aftershocks in the mantle wedge compared to the interface seismicity. We also estimate the seismic wave velocities Vp and Vs according to the amount of serpentinization and compare to the results of recent high quality tomography images. We estimate that the region of active seismicity, located mainly between 450-550°C isotherms, corresponds to a partially serpentinized part of the mantle wedge while the corner of the cold nose, which corresponds to a fully serpentinized zone, is deprived from earthquakes.

Recent great subduction earthquakes have been preceded by an accelerated rate of both interface seismicity along the megathrust and intermediate depth seismicity within the slab at ~100km depth (e.g. Bouchon et al., 2016, 2018), sometimes along with seismicity lineaments along dip over some hours (Bouchon et al., 2022, 2023). These may also be associated with large-scale gravity and mass changes in the subduction zone (Panet el al. 2018). Such interactions between deep and interface seismicity can last several years and can be associated with deformation within the upper plate (Durand et al., 2014; Jara et al. 2018, Rousset et al. 2023, Mitsui et al. 2021). However such interactions between deep seismicity and shallow deformation have been observed only on rare occasions. In addition, assessing better how they relate to fluid transfer and slab force balance is key to improved understanding of the driving mechanisms of the plate interface destabilization. Here we present some intriguing examples of interactions between intraslab seismicity and shallow deformation, and assess their statistical significance. We show that the occurrence of the Tohoku earthquake significantly changed the deep (>150km) seismicity rate, suggesting that this major megathrust event modified the slab equilibrium down to the lower mantle. We also revisit the interactions between intermediate-depth and shallow seismicity in the Japan trench and the northern Chile subduction zone, during the decade preceding the Tohoku-oki (Mw 9.0, 2011) and Iquique (Mw 8.2, 2014) megathrust events. Cross correlations highlight different periods with significant interactions between intermediate-depth and shallow earthquakes, including the 8 months before the Tohoku-Oki megathrust in Japan, over which multiple bursts of ~7 days are synchronized. In Chile, the 4 months preceding the Iquique megathrust also show strong interactions, with successive bursts of ~4 days. Unlike some other periods, no stress transfer implied by Mw>6 earthquakes can explain the correlations observed before both megathrust events. Clustering of the seismicity allowed to identify along-dip lineament patterns. Their occurrence rate shows a significant increase when approaching the date of the megathrusts. If only a few are observed in Chile, the numerous lineaments downdip Tohoku highlight some structures along which lineaments concentrate. These elongated seismicity features seem to connect intermediate-depth and shallow seismicity and could be explained by fluid migrations.

The Atacama segment in Northern Chile (24⁰S to 31⁰S) is a mature seismic gap with no major event (Mw≥8) since 1922. Nonetheless, the region regularly releases stress through shallow and deep slow slip events, and hosts recurring seismic swarm activity. To investigate this seismic gap and its complex seismic-aseismic behaviour, we instrumented the region with almost 200 seismic and geodetic stations between November 2020 and February 2024. Using machine learning techniques, we derived a dense, high-resolution seismicity catalog, encompassing over 165,000 events with double-difference relocated hypocenters. Within the network, we achieve relative location uncertainties below 50 m, enabling the resolution of fine-scale structures. Our catalog details the outer rise, interface, intraplate and upper plate seismicity. Furthermore, we capture anthropogenic sources from mine blasting and offshore active seismic experiments. Here, we focus on three aspects: The new slab geometry and it’s influence on the large scale seismic segmentation The fine scale space-time segmentation of the subduction interface The complex seismic swarms around the 2023 shallow slow slip event in Copiapó, highlighting in detail the underlying mechanisms of slow-to-fast earthquake interaction Our results provide a holistic view of this complex subduction zone, while at the same time giving insights into fine-scale structures and processes.

Postseismic displacements associated with the 2001 M w 8.4 Arequipa earthquake have been observed on a continuous GNSS timeseries in Arequipa for over two decades (∼30 cm on horizontal components). Using Finite Element Method (FEM), we explore the rheological properties of the South Peru subduction zone to model this temporal evolution, and we quantify the effects of the postseismic processes on the interseismic coupling assessment with viscoelastic Green's functions. Using one continuous and eight survey GNSS timeseries as constraints, we found that a Burgers rheology in the asthenosphere (Maxwell viscosity = 9 × 10 18 Pa·s, Kelvin viscosity = 5 × 10 18 Pa·s) with an elastic cold‐nose fits best the pattern. The postseismic processes affect the interseismic coupling distribution and moment deficit rate, raising their values by 9% over the South Peru segment and up to 24% in the vicinity of the 2001 Arequipa earthquake rupture. These values remain within the uncertainties from Lovery, Chlieh, et al. (2024, https://doi.org/10.1029/2023jb027114 ).

In Cascadia, the concomitance of slow slip events (SSE) and tremors during Episodic Tremor and Slip (ETS) episodes is well documented. Brittle tremor patches embedded in the ductile matrix deforming aseismically is the most common concept for the fault structure, but whether tremors and their patches impact the SSE initiation is under debate. This study focuses on 13 initiations of major Cascadia ETS. Limited observational constraints exist on the details of ETS initiation because spatiotemporal SSE inversions usually over‐smooth their temporal evolution. Scrutinizing tremors and SSE at the beginning of major ETS events gives us insights into their mechanical relationship. We directly retrieve the temporal evolution of the SSE moment by stacking sub‐daily Global Positioning System (GPS) time series at multiple sites, without slip inversions. Comparison of the GPS stack with tremor count demonstrates that SSE moment release accelerates drastically 1 day after the onset of vigorous tremor activity. On the other hand, once the SSE moment release accelerates, the tremor area expands more rapidly, suggesting that the growth of the ETS occurs through a feedback mechanism between slip and tremor once the SSE is well developed. By combining these and previous observations, we propose a conceptual model of ETS initiation: heterogeneous interface strength limits the growth of SSE with unruptured tremor patches acting as relatively high‐strength pins contributing to this heterogeneity. In other words, major ETS emerges probably only when collective tremor patches are critically stressed.

This work aims at investigating the consistency between a strain rate model and a long-term earthquake forecast at the European scale. We take advantage of the release of geodetic strain rate models by Piña-Valdés et al. (2022) and the release of the European Seismic Hazard Model 2020 (ESHM20) by Danciu et al. (2024) to compare geodetic and seismic moment rates across Europe. Seismic moments are inferred from the magnitude–frequency distributions that constitute the ESHM20 source model. We explore the full ESHM20 source model logic tree to account for epistemic uncertainties. On the geodesy side, we use the strain rates to calculate the geodetic moment for each area source zone of the hazard model, considering associated epistemic uncertainties. We show that the parameters contributing the most to the overall uncertainty in the geodetic moment rate are the distance weighting scheme used in the spatial inversion, the equation used to convert surface strain to a scalar moment rate, and the effective seismic thickness. We compare the distributions of geodetic and seismic moment rates at different geographical scales. In highly seismic activity zones, such as the Apennines in Italy, Greece, the Balkans, and the Betics in Spain, primary compatibility between seismic and geodetic moment rates is evident. Discrepancies emerge in low- to moderate-seismic-activity zones, particularly in areas affected by the Scandinavian glacial isostatic adjustment, where geodetic moment rates exceed seismic moment rates significantly. We show that considering broader zones enhances the match between geodetic and seismic moment rate distributions. In zones where ESHM20 magnitude–frequency distributions are well-constrained (established on more than 30 complete events), the distributions of seismic and geodetic moments usually overlap significantly, suggesting the potential for integrating geodetic data into hazard models, even in regions with low deformation.

The Atacama segment in Northern Chile (24°S to 31°S) is a mature seismic gap with no major event ( M w ≥ 8) since 1922. In addition to regular seismicity, around the subducting Copiapó ridge, the region hosts seismic swarms, and shallow and deep slow slip events. To characterize the fine structure of this seismic gap and its seismic‐aseismic interplay, we instrumented the region with almost 200 seismic and geodetic stations. Using machine learning, we derived a dense, high‐resolution seismicity catalog, encompassing over 165,000 events with double‐difference relocated hypocenters. Our catalog details the outer rise, interface, intraslab, crustal and mantle wedge seismicity. We infer a detailed slab geometry, showing that the flat slab is dipping toward the south with a narrower extent along dip. The slab geometry controls the intraslab seismicity, with cross‐cutting activity in the region of highest bending and a downdip limit around 105 km slab depth. Our catalog exhibits significant seismicity in the mantle wedge upper corner between 28°S and 31°S, highlighting the brittle behavior of the cold nose. On the subduction interface, interplate locking controls the updip end of the seismicity, with seismicity extending closer to the trench in low‐locking areas. On fine scales, resolved by relative uncertainties below 50 m, the subduction interface has a complex 3D structure, showing a fractal distribution of seismic patches down to a scale of tens of meters. Our results provide a holistic view of this complex subduction zone, while at the same time giving insights into fine‐scale structures and processes.

The central Apennines (Italy) are located within the geodynamically complex Central Mediterranean. Subduction and continental collision of the Adriatic plate underneath the Tyrrhenian appear to have ceased and the region is undergoing large-scale extension of 3-4 mm/yr accompanied by large normal faulting earthquakes. The main drivers of seismicity, extension and surface deformation remain unresolved, inhibiting a fundamental understanding of Apennine geology and progress towards seismic hazard assessment. Multiple driving mechanisms have been proposed, including differences in gravitational potential energy (GPE), independent motion of the Adria microplate, and large-scale uplift related to slab detachment. In terms of structure, debates continue about whether the slab has detached and whether the continental Moho's overlap. We systematically test these driving mechanisms and hypotheses by exploring different structures, forcings and rheologies through cross-scale numerical modelling. We adopt the seismo-thermo-mechanical (STM) modelling approach in a realistic 2D setup ranging from the surface to 800 km depth. The model uses a visco-elasto-plastic rheology and a strongly slip-rate dependent friction to spontaneously simulate fault growth and earthquake-like events. We start from the present-day setup in the central Apennines, integrating a geological cross-section, receiver function data and tomography. The initial temperature is based on long-term STM models and geothermal data. Results indicate that an attached slab induces thrust earthquakes onshore, uplift in the orogen and subsidence above the Adriatic downgoing plate, all of which are inconsistent with observations. Shallow slab detachment, leaving no Moho overlap, also fails to reproduce the observed surface deformation, as it lacks a driving force within the model. Among hundreds of tested models, a model with a detached slab, slab rebound in the undetached slab remnant and Tyrrhenian/Adriatic Moho overlap explains most observations in the central Apennines. This model successfully reproduces normal faulting earthquakes within the orogen and slight compression offshore in the Adriatic Sea, driven by eduction of the partially subducted upper crust. However, the resulting horizontal surface velocities are lower than observed, indicating that external forces also drive part of the extension in the Apennines. We model this by imposing an eastward motion of the Adriatic plate of 3-4 mm/yr, representing the pull by the Adria microplate. Removing the topography shows that GPE slightly contributes to near surface extension, but its influence is minor compared to other parameters. Finally, the power law rheology of the mantle plays a key role in allowing upward mantle flow near the base of the lithosphere, thereby counteracting compression induced by the downward pull of the sinking detached slab. To conclude, far-field Adriatic plate pull, eduction of the subducted upper crust and slab rebound drive extension and seismicity in the central Apennines. Knowing these drivers provides a basis for modeling the seismic cycle and advancing seismic hazard assessment.

The high topography of the central Andes (15-28 degrees S) is supported by thick crustal roots. The recent uplift of the Altiplano is often explained by crustal shortening and subsequent delamination of the lower crust, though its deep structure and plateau formation processes remain debated. The mechanism of flat subduction is also controversial in geodynamics. The well-documented transition from normal to flat subduction beneath southern Peru provides an ideal setting to investigate these processes. In this study, we present a new multi-parameter tomographic model of density, , , and beneath southern Peru. The model was obtained by inverting teleseismic P and SH waveforms recorded by temporary and permanent stations across 78 degrees W-66 degrees W and 10 degrees S-19 degrees S. Time and amplitude issues in the PeruSE data set were identified and corrected before inversion. The final model shows a normally dipping oceanic lithosphere in the south, with a continuous transition to flat subduction beneath central Peru, without a slab tear. The flat subducting lithosphere appears anomalously thin and hot, likely reflecting thermal erosion associated with the formation of the Nazca Ridge. This suggests that the buoyancy of the flat slab is not due to crustal thickening and delayed eclogitization reactions, as previously hypothesized, but rather to a thermally eroded and thinned oceanic lithosphere. We also detect a thin forearc crust (14 degrees S-19 degrees S) overlying a thick, cold mantle wedge. The Altiplano thickening may result from squeezing the crust between this strong forearc block and the Amazonian craton. Finally, the mantle lithosphere beneath the Altiplano is abnormally thin or absent, suggesting partial removal or delamination, which could explain the regional uplift over the past 10 Ma.