Sabancaya volcano is one of the most active volcanoes in the Central Andes. Its ongoing eruptive process is accompanied by large-scale deformation, with activation of the Huambo-Cabanaconde fault system, marked by intense seismicity over an area of about 50 & times; 30km(2) . We present a pilot magnetotelluric survey performed in 2022, covering the Ampato-Sabancaya complex, Hualca-Hualca volcano, as well as the related system of normal faults. Our three-dimensional electrical resistivity model reveals pronounced vertical gradients and lateral contrasts at elevations above sea level, along with generally low resistivity values at depth. Seismicity at depths >4 km below sea level predominantly occurs in a low resistivity environment: 90% of seismic events occur at resistivity values below 10 Omega m. Two prominent electrical conductors (<0.5 and 2-4 Omega m) are imaged at depths 11-18 km and 3-8 km, respectively. Using petrological constraints, we interpret them as the signature of the magmatic plumbing system, connecting the Hualca-Hualca and Ampato-Sabancaya volcanoes. The deeper conductor is inferred to represent a magma reservoir situated beneath the older Hualca-Hualca volcano, consistent with long-term deformation and seismicity. It is connected to the laterally offset shallow magma chamber below Sabancaya. At depth 2-10 km, a strong conductor (<0.1 Omega m) is imaged in the Huambo-Cabanaconde fault zone. The extremely high conductivity of this body is attributed to the abundance of ultra-saline brines, originating from the deep magma reservoir below. We speculate that the strong seismicity cluster detected in 2013 facilitated the passage of magmatic fluids exsolved from the magma reservoir, and replenished this ultra-conductive body.

Volcan Misti, situated in the Central Volcanic Zone (CVZ) is considered one of the most hazardous volcanoes in South America. Petrophysical and mineralogical studies of the erupted materials inferred the presence of an interactive and stratified magmatic system, composed of two to three magma reservoirs. However, its geometry and the relationships with tectonic and seismic activity remain largely unresolved due to the lack of high-resolution geophysical imaging. To address this question, 42 broadband magnetotelluric (MT) stations were deployed around the volcanic edifice to construct the first three-dimensional electrical resistivity model of the magmatic and hydrothermal system. The data were inverted and the resulting model was characterized by three low-resistivity features. The first is a conductive layer, similar to 1 km thick (5 to 40 Omega m), that extends laterally beneath the volcanic edifice and is interpreted as a clay cap. The second feature corresponds to an inferred low-resistivity body (10-30 Omega m), located at sea level. The third is a low-resistivity body (< 10 Omega m) imaged at similar to 10 km below sea level, located slightly east of the volcano (similar to 2.5 km). The resistivity of this feature is interpreted as indicative of the presence of andesitic melts, suggesting a melt fraction in the range 4-24% for the temperature range 900-950 degrees C. The seismicity associated with the volcano is minimal and concentrated just beneath the crater at a depth of similar to 2.5 km. The shallow depth of the seismicity, together with the MT model, suggests that the recharge and supply of magma occur in a cryptic manner.

Tsunami warning systems implemented worldwide rely on the fast characterization of earthquake sources, in particular on the estimation of the moment magnitude $\textit {M}_{\textrm {w}}$. Reliable estimation of $\textit {M}_{\textrm {w}}$ typically takes 10 to 20 min for large events based on conventional seismic signals. A promising alternative is the use of prompt elasto-gravity signals (PEGS), which are very low-amplitude gravitational perturbations induced by earthquakes that travel at the speed of light and can be recorded by broad-band seismometers at timescales of a few minutes after origin time. We propose here a first implementation of real-time PEGS analysis to enhance the Peruvian earthquake monitoring system by enabling rapid magnitude estimation for large and potentially tsunamigenic earthquakes. We train a graph neural network to recognize the space-time structure of PEGS over a large international set of broad-band seismic stations, even when their amplitudes are smaller than the noise level, and to rapidly estimate the magnitude and location of the source. Our results indicate that the PEGS-based system can estimate the magnitude of $\textit {M}_{\textrm {w}} \ge 8.2$ earthquakes, within 5 min after the event's initiation, with sufficient accuracy for tsunami warning purposes. Simulated real-time tests confirm the viability of the PEGS-based approach for operational early warning, providing robust source estimations of large magnitude events to the Peruvian earthquake monitoring system that are valuable for tsunami warning.

The Central Andes are a place of considerable interest for the study of the physical processes involved in subduction. Indeed, it hosts significant seismic events relatively frequently, with four earthquakes of magnitude greater than eight in the last three decades: the 1995 Mw8.0 Antofagasta, the 2001 Mw8.4 Arequipa, the 2007 Mw8.0 Pisco, and the 2014 Mw8.1 Iquique earthquakes. In addition, structural heterogeneities, such as the Nazca and Perdida oceanic ridges, appear to segment seismic ruptures along the Peru-Chile trench. Estimating the seismogenic potential of the Central Andes, particularly in Southern Peru, where the amount of geodetic data available has increased considerably in recent years, is therefore a key issue.Using 200+ GNSS sites, and InSAR mean velocity maps (2015-2021) processed in the framework of the FLATSIM Andes project (FormaTerre, 2020), we measured the deformation of the overriding plate on the horizontal and vertical components. In order to model interseismic and postseismic processes with a realistic structure and rheology, we developed a finite element method model of the subduction, featuring Newtonian viscoelastic Burgers rheology in the asthenosphere and an elastic cold nose. Accounting for the postseismic displacements associated with great subduction earthquakes, we propose a viscoelastic interseismic coupling model with unprecedented resolution in the area. This model shows significant heterogeneity, with high coupling off the coast of South Peru and Chile, and weaker coupling where oceanic structures, notably the Nazca Ridge and the Nazca Fracture Zone, subduct beneath the South American continent.The spatial resolution provided by InSAR, notably on the vertical component, is of great interest to investigate the partitioning of the deformation in the upper plate, which is a fundamental aspect in the perspective of a unified interseismic coupling model at the scale of Peru and Chile. For this purpose, we quantified the East and vertical displacements across the Cuzco fault system (up to 3 mm/yr and 2 mm/yr on the East and vertical components respectively) and the Cordillera Blanca (up to 1.5 mm/yr and 3 mm/yr on the East and vertical components respectively), which have been proposed by Villegas-Lanza et al., 2016 to delimitate a rigid block motion referred as the Peruvian Sliver. In addition to this partitioning at crustal structures, primary (3-4 mm/yr) and secondary (2 mm/yr) zones of uplift are observed in Peru and Chile, at about 130 and 250 km from the trench, respectively. The secondary zone of uplift is associated with high topography, suggesting partial interseismic plastic deformation of the upper plate. Also, the secondary uplift zone in Peru is primarily observed in the flat-slab region and tapers with the transition to dipping-slab. Both the primary and secondary uplift zones are collocated with trench-parallel stripes of intraslab seismicity, which could be linked to fluid migration processes or fracturing of the slab.

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.

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 ).

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.

We present the implementation and testing of the seismological components of the Peruvian earthquake early warning system (Sistema de Alerta S & iacute;smica Peruano [SASPe]). SASPe is designed to send alert messages to areas located within a given distance from the epicenter of large (magnitude >= 6.0) subduction earthquakes, with a first alert based on data available 3 s after the arrival of the P wave on the nearest station. The system comprises a dedicated network of 111 strong motion stations installed along the Peruvian coast. During over 2 yr of testing, the magnitude estimates are virtually unbiased, with no false positives or false negatives. In the most critical virtual scenarios of earthquakes occurring within 57 km of populated areas, SASPe can provide user lead times of up to 8 s. For more distant areas (from 70 to 120 km), lead times range from 10 to 20 s. Once the construction of the alert broadcasting system by the civil defense authority is finalized, SASPe will provide warning to 18 million residents of the coast of Peru. We validate the algorithm of the system on recent major earthquakes in Peru and other regions, demonstrating its effectiveness and versatility for global deployment.

The southern Peru subduction zone is a complex region, marking the transition between the flat slab associated with the Nazca Ridge subduction in the North and a much steeper subduction in the south. The area has been affected by several large earthquakes over the past 20 years, like the Mw 7.2 earthquake that occurred on June 28th 2024 close to the city of Acari, in an area that already ruptured in 2013 and 2018. 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 the detection and picking of phases and PyOcto for their association, we obtain a total of 154645 events. These earthquakes are located with NonLinLoc using a new 3D P and S-wave velocity model of the region obtained from full-waveform inversion. They are then relocated using double difference methods with cross-correlation times to obtain precise locations. This allows us to image seismic structures along the subduction zones, thus demonstrating the influence of interseismic coupling and of bathymetric features like the Nazca Ridge on seismicity patterns. We focus in particular on the Acari sequence, which occurred at the edge of the Nazca Ridge. The Mw 7.2 mainshock was preceded by a Mw 6 foreshock on June 16th 2024, with both earthquakes seemingly occurring at the plate interface. We show that both the foreshock and the mainshock activated intraslab seismicity along the whole edge of the ridge down to 100 km depth, thus providing a good example of far-field interactions between deep and shallow regions of the subduction.

Abstract In the central region of Peru, two earthquakes with magnitudes of Ms 5.6 and 6.2 occurred in 1969, originating from the Huaytapallana fault. As a result, two fault scarps formed on the surface: the first measuring 4 km and the second one 9.5 km in length, separated by a 4 km section without a surface scarp. A three-year seismic campaign (2015–2018) conducted around the Huaytapallana fault has provided insights into its current dynamics. The 172 microearthquakes recorded, with magnitudes ranging from Mw 0.6 to 3.1, are distributed along the northeastern flank of the fault and extend over 40 km, including segments without visible surface scarps. The Huaytapallana fault is estimated to have a depth of around 15 km with a dip of 60° toward the northeast. The composite focal mechanisms indicate a deformation process due to compression, with a fault plane oriented in the north-northwest–south-southeast direction and dipping toward the northeast at angles between 55° and 60°. The Mw 4.7 earthquake in 2022 and its series of aftershocks exhibit a similar deformation pattern associated with the Huaytapallana fault. These results are consistent with the regional tectonics, which control the deformation processes in the Mantaro basin, originating from the convergence of the Nazca and South American plates. We consider that the significant microseismic activity occurring in areas without visible surface scarps suggests the accumulation of substantial deformation, which could lead to future earthquakes of greater magnitude that may cause significant surface displacements.

We determined the main parameters of the source rupture process of intermediate- and deep-depth earthquakes occurring in the Peru–Brazil–Bolivia border region and northern Chile. The parameters of depth, fault-plane orientation, scalar seismic moment, slip distribution, and radiated seismic energy are obtained from seismograms. We selected 15 intermediate-depth earthquakes (100 km < h < 300 km) and 10 very deep earthquakes (h > 500 km) with magnitudes MW ≥ 6.0. For most events, the slip distribution over the rupture plane shows a single asperity, and the source time function presents a simple pulse. There are differences between intermediate-depth and deep earthquakes. The rupture areas, maximum slip and source time function (STF) duration are larger for intermediate-depth events than for deep events. Additionally, the STF’s show a sharper increase for deep earthquakes. The scaled radiated seismic energy shows larger values for deep depth events. The stress regime pattern derived from the obtained focal mechanism agrees with the geometry of the subduction of the Nazca plate. At intermediate depths, in the northern area up to 12°S, the stress pattern corresponds to a horizontal extension, while in the southern area, the tension axes dip at an angle of 30°. At deep depths, the stress regime corresponds to vertical compression in the north and dips of approximately 45° in the south.

The Central Andes subduction has been the theater of numerous large earthquakes since the beginning of the 21st Century, notably the 2001 Mw = 8.4 Arequipa, 2007 Mw = 8.0 Pisco and 2014 Mw = 8.1 Iquique earthquakes. We present an analysis of 47 permanent and 26 survey global navigation satellite system (GNSS) measurements acquired in Central-South Peru between 2007 and 2022 to better understand the frictional properties of the megathrust interface. Using a trajectory model that mimics the different phases of the cycle, we extract a coherent interseismic GNSS field at the scale of the Central Andes from Lima to Arica (12-18.5 degrees S). Interseismic models on a 3D slab geometry indicate that the locking level is relatively high and concentrated between 20 and 40-km depth. Locking distributions indicate a high spatial variability of the coupling along the trench, with the presence of many locked patches that spatially correlate with the seismotectonic segmentation. Our study confirms the presence of a creeping segment where the Nazca Ridge is subducting; we also observe a lighter apparent decrease of coupling related to the Nazca Fracture Zone (NFZ). However, since the Nazca Ridge appears to behave as a strong barrier, the NFZ is less efficient to arrest seismic rupture propagation. Considering various uncertainty factors, we discuss the implication of our coupling estimates with size and timing of large megathrust earthquakes considering both deterministic and probabilistic approaches. We estimate that the South Peru segment could have a Mw = 8.4-9.0 earthquake potential depending principally on the considered seismic catalog and the seismic/aseismic slip ratio. Using dense global navigation satellite system (GNSS) data collected in the South-Central Peru, we extracted a large scale interseismic velocity (surface velocity between two earthquakes) field at the scale of the Central Andes of Peru, where the oceanic Nazca plate goes under the continental South America plate at a velocity of about 6 cm/yr. This area has been the theater of several great subduction earthquakes and tsunamis, then estimating the stress build-up on the subduction interface is key to better anticipate future large earthquakes. Through a modeling of the GNSS velocities on a 3D slab geometry, we were able to obtain useful informations on the location, size, magnitude and return period of future great earthquakes in South Peru. Thereby, we obtained a very heterogeneous spatial distribution of interseismic coupling (degree of locking between the two tectonic plates), with low-coupled areas where the Nazca Ridge and the Nazca Fracture Zone are subducting, but highly-coupled areas close to the coasts of Lima and Arequipa. Finally, we estimate that the South Peru segment between the Nazca Ridge and the Arica band could have the potential to host a Mw = 8.4 to Mw = 9.0 earthquake, with a one century and one millennial recurrence time respectively. We present a dense interseismic velocity field at the scale of the South Peruvian Andes, from new decadal global navigation satellite system data at 73 locations Low locking (similar to 0.4) is estimated along the Nazca Ridge and the Nazca Fracture Zone, delimiting wide patches of high locking (similar to 0.9) Moment budget analysis shows that the South Peru segment could host a Mw = 8.4-9.0 earthquake with a 100 to 1,000 years recurrence time

We have estimated the source mechanisms of 15 intermediate (100 < h < 300 km) and 11 deep (h> 500 km) depth earthquakes (Mw ≥ 6.0), located at the Peru-Brazil-Bolivia border. From teleseismic waveforms, using the slip inversion over the rupture plane, we have estimated the fault-plane orientation, scalar seismic moment, source time function, slip distribution, rupture velocity and stress drop. From north to south direction, for shocks located between 1 ºS and 12 ºS, the focal mechanisms of intermediate and deep events correspond to normal faulting with horizontal extension approximately in E-W direction. In this region, the Nazca plate, moves as a flat slab at a depth of 120 km between 400 km to 600 km distances from the trench. At greater distances from the trench, the Nazca plate begins to dip. Further south, from 13 ºS to 20ºS, the tension axes present a greater dip for intermediate earthquakes, in agreement with the change from flat to dipping subduction. We do not observe any significant difference between the, slip distribution, STF, rupture velocity and stress drop for intermediate and deep earthquakes. The stress drop shows values with slight differences between the northern group (1 ºS - 12 ºS) of earthquakes and the southern one (13 ºS - 20ºS). The shape of the source time functions of intermediate and deep earthquake presents a depth dependence in agreement with the conclusions of other studies. The source time functions of intermediate events are more complex than those of deep ones and present a longer mean duration. From these results we present a stress pattern scheme of the slab, showing at intermediate depth a horizontal extension in the northern part correlated to the flat slab, and with vertical compression for deeper events. In the southern part there are dipping extensions at intermediate depth and dipping compressions at a deep depth.

We introduce the Ensemble Earthquake Early Warning System (E3WS), a set of Machine Learning algorithms designed to detect, locate and estimate the magnitude of an earthquake using 3 seconds (or more) of P waves recorded by a single station. The system is made of 6 Ensemble Machine Learning algorithms trained on attributes computed from ground acceleration time series in the temporal, spectral and cepstral domains. The training set comprises datasets from Peru, Chile, Japan, and the STEAD global dataset. E3WS consists of three sequential stages: detection, P-phase picking and source characterization. The latter involves magnitude, epicentral distance, depth and back-azimuth estimation. E3WS achieves an overall success rate in the discrimination between earthquakes and noise of 99.9%. For P-phase picking, the Mean Absolute Error (MAE) is 0.14s. For source characterization, the MAEs for magnitude, distance, depth and back-azimuth are 0.34 magnitude units, 27 km, 15.7 km and 45.2°, respectively. By updating estimates every second, the approach gives time-dependent magnitude estimates that follow the earthquake source time function. E3WS gives faster estimates than present alert systems, providing additional valuable seconds for potential protective actions.

SUMMARYIn the central region of Peru, two earthquakes with magnitudes of M5.6 and M6.2 occurred in 1969 with origin in the Huaytapallana fault and as a result, two fault scarps of 4 and 9.5 km in length were formed on the surface, separated by a 4 km section without fault scarp. A 3-year seismic campaign carried out around the Huaytapallana fault has allowed us to know its current dynamics. The recorded earthquakes are distributed on the northeast flank of the fault and along 40 km, including the sections without visible surface scarps. The Huaytapallana fault would have a depth of 25 km with a dip of 60° in a northeast direction. The composite focal mechanisms indicate a compressional deformation process and a fault plane-oriented NNW-SSE with dip in NE direction with an average angle of 56°. The results obtained are consistent with the active tectonics of the study area and with the rupture processes associated with the 1969 earthquakes. The concentration of earthquakes in areas without a visible fault scarp on the surface would indicate that stresses and deformation are accumulating that in the future would give rise to new earthquakes similar to those of 1969.

Sabancaya volcano is the youngest and second most active volcano in Peru. It is part of the Ampato-Sabancaya volcanic complex which sits to the south of the ancient Hualca Hualca volcano and several frequently active faults, thus resulting in complex volcano-tectonic interactions. After 15 years of repose, in 2013, a series of 4 earthquakes with magnitude >4.5 occurred within 24 h, marking the beginning of a new episode of unrest. Several additional swarms of earthquakes occurred in the following years until magmatic eruptive activity started on 6 November 2016. This activity is ongoing as of this writing, with an average of 50 explosions per day. In this study, we present results of multiparametric monitoring of Sabancaya's activity observed during 2013-2020. Seismic data are used to create a one-dimensional seismic velocity model, to catalog, locate, and characterize earthquakes, to detect repeating earthquake families, and to monitor seismic velocity variations by ambient noise cross-correlation. These analyses are complemented by visual and remote sensing observations and ground deformation measurements. All monitored parameters showed significant changes on 6 November 2016, the day of eruption onset, thus dividing the eruptive activity into pre-eruptive and eruptive stages.The unrest is characterized by high levels of seismic activity with hundreds of events detected per day. Volcano-tectonic (VT) earthquakes were dominant during the pre-eruptive period while long-period (LP) events and explosions have been most numerous since the eruption onset. Earthquake locations highlight long-lasting seismogenic zones along multiple previously active regional faults, as well as along newly identified faults. This VT seismicity is mainly distributed in a sector from the northwest to the east of the volcanic complex at distances of up to 30 km from the crater. We focus our analysis on two eruptive episodes: the eruption onset and subsequent crater migration from south to north, and the increase of lava dome extrusion rate in 2019. Both episodes are accompanied by seismic velocity decreases of up to 0.2% and are preceded by a few weeks by bursts of distal VT activity, including numerous repeating earthquakes. These repeated events were located on several remote tectonic faults (5-25 km from the vent). We suggest that these phenomena could be due to the injection of a batch of magma in the deep reservoir and/or conduit, which would generate 1) a pressure wave propagating in the hydrothermal system, triggering the bursts of seismic activity and 2) slow rising of magma by melting old material filling the conduit that eventually produced the eruptive and dome growth acceleration events.

We present a multi-disciplinary study of the rupture process of deep- and intermediate-depth earthquakes in the subducting slab that develops beneath the Peruvian-Brazilian region. This contemplates the understanding of the atomistic fracture mechanism in an olivine model, its energetics budget, and the bridging of these results to the available seismic observables. A theoretical description of the stress-strain curves for the subducting material is initially provided as a key element to discern whether the rupture mechanism changes with depth or not. To this purpose, atomistic modelling was carried out through ab initio techniques for the forsterite olivine at different pressure ranges. The achieved stress-strain curves were compared to the average moment-scaled functions obtained for 43 intermediate (50 km < h < 200 km) and very deep earthquakes (500 km < h < 700 km) at the Peruvian-Brazilian subduction zone. It is found that at both depths operate a common atomistic rupture mechanism that is based on the gliding of the {001} crystal planes. Although the velocity of stress release changes with depth, this finding helps to clarify the controversial rupture process for very deep earthquakes at subduction zones. Likewise, efforts were directed to quantify the total amount of energy freed during an earthquake. Test calculations were carried out for several deep earthquakes providing rupture energy of six orders of magnitudes larger than the observable radiated seismic energy. This indicates that there might be space for redefining the commonly accepted order of magnitude for the seismic efficiency coefficient.