Seismic Changes Research Articles

Co- and post-seismic deformation of the 2022 Menyuan Mw6.6 earthquake from InSAR and GPS observations

Summary This study combines InSAR and GPS data to examine the co-seismic slip and post-seismic deformation of the 2022 Menyuan Mw6.6 earthquake, shedding light on the fault structure, slip distribution, and rheology of the northeastern Tibetan Plateau. InSAR co-seismic deformation revealed fault dip angle of 82° for the Lenglongling fault and 84° for the Tuolaishan fault. The optimal co-seismic slip model, derived from InSAR, GPS, and near-field pixel-offset data, indicates a maximum slip of 3.3 m, concentrated in the upper 3 km of the fault. We propose a three-step procedure to comprehensively invert the post-seismic deformation, accounting for both afterslip and viscoelastic relaxation, constrained by the InSAR and GPS observations. The optimal afterslip model indicates a cumulative afterslip of 9 cm over two years, primarily concentrated in the deeper sections of the co-seismic slip zone. Incorporating viscoelastic relaxation improved the spatial distribution of the afterslip on the Tuolaishan fault. The afterslip released a seismic moment of 1.96 × 10¹⁸ Nm, accounting for approximately 15 per cent of the co-seismic moment release. The viscosity of the lower crust in the region was estimated to range from 1.5 to 5 × 1018 Pa·s, with an optimal value of 2 × 10¹⁸ Pa·s. As the distance from the epicenter increased, viscoelastic relaxation became the dominant post-seismic mechanism, contributing up to 80 per cent of the deformation observed at the QHGC and GSMI stations. Additionally, the earthquake increased Coulomb stress on the ‘Tianzhu Seismic Gap’ and nearby faults, raising seismic hazard in the region. These findings highlight the importance of simultaneously considering both afterslip and viscoelastic relaxation mechanisms in post-seismic deformation analysis, and accounting for post-seismic effects when evaluating seismic stress changes.

Triggering the 2022 eruption of Mauna Loa.

Distinguishing periods of intermittent unrest from the run-up to eruption is a major challenge at volcanoes around the globe. Comparing multidisciplinary monitoring data with mineral chemistry that records the physical and spatio-temporal evolution of magmas fundamentally advances our ability to forecast eruptions. The recent eruption of Mauna Loa, Earth's largest active volcano, provides a unique opportunity to differentiate unrest from run-up and improve forecasting of future eruptions. After decades of intermittent seismic and geodetic activity over 38 years of repose, Mauna Loa began erupting on 27 November 2022. Here we present a multidisciplinary synthesis that tracks the spatio-temporal evolution of precursory activity by integrating mineral and melt chemistry, fluid inclusion barometry, numerical modeling of mineral zoning, syn-eruptive gas plume measurements, the distribution and frequency of earthquake hypocenters, seismic velocity changes, and ground deformation. These diverse data indicate that the eruption occurred following a 2-month period of sustained magma intrusion from depths of 3-5 km up to 1-2 km beneath the summit caldera, providing a new model of the plumbing system at this very high threat volcano. Careful correlation of both the geochemistry and instrumental monitoring data improves our ability to distinguish unrest from the run-up to eruption by providing deeper understanding of the both the monitoring data and the magmatic system-an approach that could be applied at other volcanic systems worldwide.

‘Un oubli généreux du passé’: Art, Politics and Oblivion, and the Salon of 1814

Abstract The collapse of Napoleon’s Empire and the restoration of Louis XVIII left a legacy so embittered that hopes of political reconciliation were thought impossible. To this end, the new constitution required that the atrocities of the past were simply ‘forgotten’. Artists responded to the call in a wide variety of ways: pictures of the nation’s ancient past, depictions of a sacral monarchy and images of domesticity had a renewed appeal and offered a narrative refuge from the traumatic memories of the Republic and Empire. But art’s relationship with criticism and politics was by no means stable. This essay examines the myriad ways in which the policy of ‘l’oubli’ shaped the production and interpretation of the pictures shown at the Salon of 1814, and the entangled, fragmented and contingent ties between art, politics, history and criticism at a moment of seismic political change.

The changing roles of scientific journals.

After centuries of relative stability, the scientific publishing world has undergone tremendous disruption and change during the first decades of the 21st century. The causes for disruption can be traced to the information revolution, which brought such benefits as rapid publication, greater connectivity, and ready access to large databases, along with less desirable practices including image manipulation, plagiarism, and other ethical transgressions. The information revolution has driven the proliferation of journals, expansion of for-profit academic publishing, and empowerment of the open-access movement, each of which has exerted new financial pressures on traditional publishing models. As journals became the focal point for ethical concerns in science, they have adapted by increasing the scope of their duties, which now include archiving of data, enforcement of good practices, establishment of standards for rigor, and training the next generation of reviewers and editors. Here, we consider the seismic changes occurring in scientific publishing and place them into the context of a rapidly changing landscape of scientific and publishing norms.

Moving toward Bank 4.0 in India: a qualitative thematic analysis and future research agenda

Purpose The banking sector is more revolutionized than ever, with advanced technologies driving a seismic change in the financial industry. This study aims to understand how digital technologies influence banking sector employees and their perception of working in an era of Banking 4.0. Design/methodology/approach This study incorporated qualitative analysis to gain different insights from diverse respondents from banking industries. A purposive sampling method was adopted, and semistructured interviews were conducted, taking a sample of 72 respondents. All the transcripts were then analyzed using NVivo. Findings The findings focus on challenges related to understanding technology phenomena, managing changes, infrastructure, skills, competitiveness and regulatory mechanisms. This is further followed by the favorable impact of Banking 4.0 on employees and future avenues, such as innovation in financial services, work productivity, career opportunities and change management, banking 4.0 and banking 5.0, and banking 4.0 management strategies identified as the significant findings. Practical implications This study provides guidelines for Banking 4.0 provision strategy and conceptual reference toward the development of Banking 4.0. It also supports the Enhanced Access and Service Excellence 4.0 program, driven by the Indian Bank’s Association, to focus more on digitization, automation and data analytics. Originality/value The novelty of this research provides a qualitative hierarchy of significant challenges, favorable impacts and future research avenues of Banking 4.0 in the Indian banking sector.

Estimation of seismometer clock time offsets using Kalman Filter towards accurate seismic velocity change

SUMMARY Monitoring seismic velocity changes obtained from ambient noise correlations is widely used to understand changes in rock properties in response to earthquakes, volcanic activities and environmental changes. Since continuous seismic data have been accumulated, this method can estimate long-term changes in seismic velocity, such as crustal recovery after a major earthquake and temporal variations in seismic velocity related to long-term environmental change. Changes in seismic velocity can be estimated with a high temporal resolution by measuring the phase differences of ambient noise correlations based on a seismic interferometry method. Still, these phase differences are influenced not only by seismic wave velocity changes but also by errors in clock timing in seismometers. The clock drift occurs due to out-of-synchronization with the GPS clock and the drift of the internal clock. Therefore, to accurately monitor temporal changes in crustal structure by measuring the phase differences of noise correlations, it is crucial to evaluate the contribution of errors in clock timing to the phase differences. Recently, a method using an extended Kalman filter based on a state-space model was developed for reliable detection of temporal changes in the waveforms of ambient noise correlations, with the state-space model offering the advantage of flexible modelling of time-series data. In this study, we incorporated the time-shifts caused by clock time errors of the seismometer into the state-space model of the temporal changes in ambient noise correlations. We estimated seismic velocity changes, amplitude changes of noise correlations and clock time errors from 2010 April to 2021 September at seismic stations around the Shinmoe-dake volcano in Japan, which experienced eruptions in 2011 and 2018, respectively. Several stations exhibited clear clock time offsets, and the occurrence of clock time-shifts coincided with the dates when the data logger was turned off for seismic station maintenance or replacement of the seismometer. The proposed method provides stable estimations with respect to the signal-to-noise ratio of the waveform, and this stable estimation facilitates accurate timing of seismic recordings, enabling precise analysis of seismic phase arrival times.

Tidally modulated seismic velocity changes observed using submarine dark fiber and the virtual-source method

Natural cyclical stress perturbations, including wet and solid earth tides, coupled with repeatable seismic monitoring approaches, provide a tool for understanding the elastic properties of rocks at depth. Ocean tides, in particular, perturb the overburden and pore pressure, affecting hydraulic and elastic rock properties. The recent emergence of distributed acoustic sensing (DAS) and seismology using existing dark telecom fiber offers an unprecedented opportunity to instrument the seas and oceans with seismic monitoring networks of large aperture, fine spatial resolution, and broadband sensitivity. We use a submarine dark-fiber array to methodologically assess whether the changes in seafloor seismic velocities are modulated by ocean tidal loading. Considering oceanic ambient noise (AN) in the frequency range between 1 and 5 Hz, we find it possible to retrieve reliable surface-wave estimates using relatively short time windows (approximately 60 min). Next, using the power of linear arrays to capture AN energy from the stationary-phase zones and AN processing techniques commonly used in DAS applications for subsurface monitoring in urban settings, we introduce a methodological approach to turn each segment of dark fiber into a short-offset monitoring array (2 km), providing redundant, hourly, surface-wave estimates. Using four days of AN data recorded by the Monterey Accelerated Research System (MARS) 20 km section offshore cable, we generate the virtual-source gathers for 10 segments spanning the whole MARS cable. We then use virtual-source data from one segment to estimate the hourly velocity changes that are then quantitatively compared with the tidal data. The results suggest that changes in seafloor seismic velocities are likely modulated by tidal height, even in regions without large tidal excursions. This advance demonstrates a new application of submarine telecom fibers for monitoring the seismic stress response of near-seafloor sediments.

Sustained Co‐Eruptive Increase in Seismic Velocity Below Great Sitkin Volcano Due To Magma Extrusion

AbstractVolcanic eruptions carry essential information on the dynamics of volcanic systems. Studies have documented variable eruption styles and eruptive surface deformation. However, co‐eruptive subsurface structural changes remain poorly understood. Here we characterize the seismic velocity changes from July 2019 to July 2023 at Great Sitkin Volcano in the central Aleutian volcanic arc, using single‐station ambient noise interferometry at five three‐component seismic stations. Coincident with the lava effusion since late July 2021, about two months after the explosive eruption on 26 May 2021, we observe a sustained velocity increase, most prominently to the northwest of the caldera. We attribute this velocity increase to the structural changes with magma extrusion, with the spatial variation controlled by the geometry of the magma system or the property of shallow volcaniclastics. Our findings offer insights into understanding co‐eruptive structural modifications at active volcanoes.

Seismicity changes and numerical simulation of coseismic deformation following the 2022 Ms6.8 Luding earthquake in Sichuan, China

Seismicity changes and numerical simulation of coseismic deformation following the 2022 Ms6.8 Luding earthquake in Sichuan, China

“The Game Was Ruined For Me There:" Examining the Mental Health Byproducts of the Transfer Portal and NIL on Student-Athletes

Two rule changes have brought seismic changes to collegiate sports in the United States—the right for college athletes to monetize their Name, Image, and Likeness (NIL), and the Transfer Portal for athletes looking to switch schools. Qualitative interviews with 16 college athletes, explored the mental health byproducts of these new athlete opportunities. The interviews suggest that many athletes are hesitant to participate in NIL due to a lack of guidance. The study also found that college athletes believe entering the Transfer Portal to be a highly stressful experience, comparing the process to being recruited out of high school. However, the accessibility of the Transfer Portal also helps students leave situations that are negatively impacting their mental health faster and easier than before. Since college athletes are a highly at-risk demographic of college athletes for mental health issues, their first-hand perspective can help on-campus staff and administrators have a better understanding of what is needed to give collegiate athletes the best possible experience to learn and develop as students and citizens.

궁정 작가와 귀족 여성의 ‘정치적 우애’로 보는 카롤루스 궁정 문화

Through Carolus Magnus’ four successive marriages and cohabitations, the court of Carolus established itself as a close-knit kinship community crowded with sons, daughters, and grandchildren. Carolus Magnus, the so-called head of the three generations, did not want his beloved daughters to marry. However, the court of Carolus began to be filled with the daughters of Carolus Magnus and those who supported them or had a special relationship with them. The daughters of Carolus Magnus, who had the closest contact with their great father(pater optimus) at the court of Carolus, developed their own personal network and political influence through informal relationships. The ‘political friendship(amicitia)’ between the noble women of the Carolingian court and the court writers began to create new changes within the Carolingian court. The beloved daughters of Carolus Magnus, who were born and raised at the court of Carolus, could not escape the patriarchal order of Carolus Magnus. As their father intended, the beautiful women could not leave the court like decorations that beautified the Carolus court and were like a kind of display that visually showed the power and wealth of the Carolus Empire. The death of his great father, Carolus Magnus, in 814 brought about a seismic change in the Carolingian court, the heart of the Carolingian Empire and a place of political memory. Ludovicus, the pious king, brought out from the center of the court his sisters who had beautifully illuminated the court. In this study, we trace the political moves of the wives and beloved daughters of Carolus Magnus, who led court culture, through the eyes of the 8th and 9th century Carolus court poets and biographer. This study seeks to reexamine the political dynamics and conflicts between the women who filled the court of Carolus and their political supporters or lovers, and furthermore, the political and historical meaning of the culture of the court of Carolus.

Temporal variations of the ‘in-situ’ nonlinear behaviour of shallow sediments during the 2016 Kumamoto Earthquake sequence

SUMMARY Strong ground shaking has the potential to generate significant dynamic strains in shallow materials such as soils and sediments, thereby inducing nonlinear site response resulting in changes in near-surface materials. The nonlinear behaviour of these materials can be characterized by an increase in wave attenuation and a decrease in the resonant frequency of the soil; these effects are attributed to increased material damping and decreased seismic wave propagation velocity, respectively. This study investigates the ‘in-situ’ seismic velocity changes and the predominant ground motion frequency evolution during the 2016 Kumamoto earthquake sequence. This sequence includes two foreshocks (Mw 6 and Mw 6.2) followed by a mainshock (Mw 7.2) that occurred 24 hr after the last foreshock. We present the results of the seismic velocity evolution during these earthquakes for seismological records collected by the KiK-net (32 stations) and K-NET (88 stations) networks between 2002 and 2020. We analyse the impulse response and autocorrelation functions to investigate the nonlinear response in near-surface materials. By comparing the results of the impulse response and autocorrelation functions, we observe that a nonlinear response occurs in near-surface materials. We then quantify the velocity reductions that occur before, during, and after the mainshock using both approaches. This allows us to estimate the ‘in-situ’ shear modulus reduction for different site classes based on V$_{S30}$ values (V$_{S30}\lt 360$ m s−1, $360\lt $V$_{S30}\lt 760$ m s−1 and V$_{S30}\gt 760$ m s−1). We also establish the relationships between velocity changes, shear modulus reduction, variations in predominant ground motion frequencies and site characteristics (V$_{S30}$). The results of this analysis can be applied to site-specific ground motion modelling, site response analysis and the incorporation of nonlinear site terms into ground motion models.

(053) THE CONSORTIUM FOR THE STUDY OF WOMEN’S SEXUAL WELLNESS: RATIONAL, MISSION AND CALL TO ACTION

Abstract Introduction Female sexual wellness products have been growing and this growth was accelerated during the pandemic and the increased interest in self-care. While trying to find a place in beauty, sexual wellness really is only slightly beauty-adjacent. The beauty industry is built on delivering many products based solely on a promise. Little science is applied in this field to show any MOA or clinical efficacy. However, even in this sector the status quo is being disrupted by the FDAs Modernization of Cosmetic Regulations Act of 2022 (MoCRA). However, sexual wellness products are really more pharma-adjacent, even while using non-pharmaceuticals (nutraceuticals) ingredients. We reviewed all non-device based sexual wellness products that claimed functional benefit and based on these results, we make some recommendations. Objective To challenge the female sexual wellness industry to adopt basic and clinical science in the development and marketing of female sexual wellness products. Methods Over a three-year span, we reviewed the ingredients and claims as well as any clinical trial data on products claiming a functional benefit in sexual desire, arousal and/or orgasm. Following the unsurprising findings, we propose a number of solutions. Results Without naming the companies or products, we found an abundance of unusual products that did not seem to have a scientific rationale for ingredients and virtually all claims were unsubstantiated. Two entities have performed clinical studies. The first is a cannabis company which performed a study without a validated instruments and soft-endpoints, and as expected, there was a 100% response rate. The second entity has performed pre-clinical studies (organ bath and MOA studies) and an open-label pilot study employing a modified FSFI and diary data and efficacy and safety output. However, this was not a randomized, double-blind, placebo-controlled study. Conclusions Seismic changes are happening in the beauty and wellness industry. Female sexual wellness is closely pharma-adjacent and, as such, should adopt the preclinical and clinical trial approach that has already been developed for the evaluation of drugs in female sexual dysfunction. While these agents may only enhance normal function and don’t treat diseases or disorders, the learnings from the last half century in sexual pharmacotherapy are readily adapted to the development and evaluation of sexual wellness products. Vella Bioscience is rapidly moving to follow these principles, as follows: 1. We are performing a three-month RCT with liposomal cannabidiol vs placebo that has been powered to demonstrate statistical and clinical significance. The outcome instruments include both the PROMIS database and diary data. 2. The establishment of the Consortium for the Study of Women’s Sexual Wellness, with the following mission: Bring scientific rigor to the basic science and clinical science research of sexual wellness products, including the utilization of double-blind, placebo-controlled, randomized clinical trials. Support research, education, and public awareness of female sexual health and wellness. Enable healthcare providers and customers to directly access research protocols and validated products for the management of sexual wellness. Critical to this mission are the members of the Scientific Advisory Board of the Consortium, including Alan Altman, MD, FACOG, Anita Clayton, MD, Peter Fodor, MD, FACS, Sheryl Kingsberg, PhD, Cindy Meston, PhD, James Pfaus, PhD, Nicole Prause, PhD, Raymond Rosen, PhD, and James Simon, MD, FACOG. We invite other corporate entities to utilize the consortium and we hope that ISSWSH will adopt these principles as well. Women deserve data and not a promise. Disclosure Yes, this is sponsored by industry/sponsor: Vella Bioscience, Inc. Clarification: Industry initiated, executed and funded study. Any of the authors act as a consultant, employee or shareholder of an industry for: Vella Bioscience, Inc.

Analyzing possible seismic velocity changes in Mexico City using seismic noise interferometry

The seismic response of the Mexico City basin has received plenty of attention as one of the most relevant cases of ground motion amplification. A recent study showed possible velocity variations of the deposits in both the lake bed and firm ground. A clear drop in seismic velocity was observed during the 2017.09.19 earthquake (Mw 7.1) in addition to more subtle seismic velocity changes related to seasonal temperature and precipitation. We use continuous seismic noise data recorded in a 29 broadband seismograph network in and around Mexico City to investigate Rayleigh wave group velocity structure and velocity changes. We estimate Green's functions (GF) between station pairs using seismic noise cross-correlation. An average estimate is computed for each of three five-day periods of recording. GFs are dominated by a Rayleigh pulse at low frequencies (between 0.1 and 0.2 Hz). Velocity changes are investigated through the comparison between GF's for different five-day periods. No velocity variations are observed. Station pairs separated at a distance smaller than 20 km also show some Rayleigh wave energy at higher frequencies, between 0.3 and 1.2 Hz. We repeated the analysis in a higher frequency band (up to 5 Hz) and show that again no velocity variation can be observed. In addition, we used horizontal-to-vertical spectral ratios computed for both earthquake and seismic noise records to identify possible non-linear effects during the 2017 earthquake. The results showed that significant non-linear effects during that event are to be discarded. Finally, we present preliminary results of a tomography of Rayleigh wave group velocity at the center of the array. Lateral structure variations below the geotechnical zonation are significant. Our data will be useful to constrain the structure of the volcanic deposits of the Transmexican Volcanic Belt (TVB).

Inner core backtracking by seismic waveform change reversals

The solid inner core, suspended within the liquid outer core and anchored by gravity, has been inferred to rotate relative to the surface of Earth or change over years to decades based on changes in seismograms from repeating earthquakes and explosions1,2. It has a rich inner structure3–6 and influences the pattern of outer core convection and therefore Earth’s magnetic field. Here we compile 143 distinct pairs of repeating earthquakes, many within 16 multiplets, built from 121 earthquakes between 1991 and 2023 in the South Sandwich Islands. We analyse their inner-core-penetrating PKIKP waves recorded on the medium-aperture arrays in northern North America. We document that many multiplets exhibit waveforms that change and then revert at later times to match earlier events. The matching waveforms reveal times at which the inner core re-occupies the same position, relative to the mantle, as it did at some time in the past. The pattern of matches, together with previous studies, demonstrates that the inner core gradually super-rotated from 2003 to 2008, and then from 2008 to 2023 sub-rotated two to three times more slowly back through the same path. These matches enable precise and unambiguous tracking of inner core progression and regression. The resolved different rates of forward and backward motion suggest that new models will be necessary for the dynamics between the inner core, outer core and mantle.

Winning with customers: Achieving differentiation in custody and asset servicing

Custodians and asset servicers continue to face headwinds from a tough macro environment and changing regulatory landscape, while being at the cusp of seismic technology changes. This includes artificial intelligence (AI), large language models (LLM) and digital ledger technology (DLT) that are delivering ground-breaking insights from vast data sources and enabling digitisation of assets that can redefine value chains. The securities services industry is constantly challenged to get the right balance between providing robust and efficient core services and innovative solutions for the future. So, amid the deluge, where should these institutions focus attention to service evolving client needs and sharpen their competitive differentiation? Should companies prioritise new value creation in core services by continuing to focus on data quality, efficiency, risk reduction and resilience initiatives using latest technologies such as AI and machine learning (ML)? Or should they focus more on augmenting the client experience with newer datadriven services and insights? Is a data-sharing and collaboration-driven platform and ecosystembased approach going to drive the future? This paper touches on some of the considerations and strategies that custodians are focusing on today to achieve client-oriented differentiation in custody and asset servicing.

Stacking of Distributed Dynamic Strain Reveals Link Between Seismic Velocity Changes and the 2020 Unrest in Reykjanes

AbstractIn this study, we measure seismic velocity variations during two cycles of crustal inflation and deflation in 2020 on the Reykjanes peninsula (SW Iceland) by applying coda wave interferometry to ambient noise recorded by distributed dynamic strain sensing (also called DAS). We present a new workflow based on spatial stacking of raw data prior to cross‐correlation which substantially improves the spatial coherency and the time resolution of measurements. Using this approach, a strong correlation between velocity changes and ground deformation (in the vertical and horizontal direction) is revealed. Our findings may be related to the infiltration of volcanic fluids at shallow depths, even though the concurrent presence of various processes complicates the reliable attribution of observations to specific geological phenomena. Our work demonstrates how the spatial resolution of DAS can be exploited to enhance existing methodologies and overcome limitations inherent in conventional seismological data sets.

Advances in undergraduate and postgraduate education- bedside, simulation and E-learning

Clinical bedside teaching the cornerstone of medical education in the 19th century has been shaped and developed by changes in healthcare delivery and work practices. Developing skilled clinicians to work and thrive in these complex environments requires innovative and adaptive strategies. In this rapidly changing environment compounded by a shorter duration of training, there is an increasing focus on the student learner, team-based working and the development of professionalism. The continuum of medical education from undergraduate through postgraduate to continued professional development has been greatly enhanced by the adoption of new strategies and technologies. Simulation is long established in medical education and its benefits well recognised. Technological developments including Artificial Intelligence have supported and enhanced the quality of simulation in medical education. There is a broad range of simulation available with varying degrees of fidelity, as required, culminating in immersive virtual reality. The challenges for medical educators of the Covid-19 pandemic, with closure or restricted access to clinical patients, wards and classrooms, resulted in rapid restructuring of teaching programs and for many to move “on-line”. This resulted in widespread rapid adoption of technologically driven medical education, with E-learning, blended learning and innovative strategies to increase student engagement. The seismic changes in medical education necessitated by the Covid-19 pandemic coupled with the upskilling of medical educators and technological advances, should result in an exciting period of continued innovation in medical education, a second “Golden Era” and enhance medical education for many years to come.

Relative Seismic Velocity Variations at Axial Seamount Observed With Ambient Seismic Noise Capture Transition Point in Volcanic Inflation

AbstractTemporal changes in seismic velocity estimated from ambient seismic noise can be utilized to infer subsurface properties at volcanic systems. In this study, we process 7 years of continuous seismic noise at Axial Seamount and use cross‐correlation functions to calculate the relative seismic velocity changes (dv/v) beneath the caldera. We find a long‐term trend of decreasing velocity during rapid inflation, followed by slight increase in velocities as background seismicity increases and inflation rate decreases. Furthermore, we observe small short‐term increases in dv/v which coincide with short‐term deflation events. Our observations of changes in dv/v and their correlation with other geophysical data provide insights into how the top ∼1 km of the crust at Axial Seamount changes in response to subsurface magma movement and capture the transition from a period of rapid reinflation to a period where the caldera wall faults become critically stressed and must rupture to accommodate further inflation.

Intermediate-depth seismicity and intraslab stress changes due to outer-rise faulting

Intermediate-depth seismicity is common in subducting slabs and the seismicity rate shows some statistically significant yet enigmatic global positive correlation with the maximal throw of outer-rise normal faults. Here, we have simulated the formation and subduction of outer-rise faults, using 2D thermomechanical numerical models of intra-oceanic subduction with coupled brittle-ductile damage of bending plates. We observed that outer-rise faults are formed episodically during slab segmentation and their maximal throw grows with time. When been subducted to intermediate depth, these faults are locally reactivated either by i) slab unbending/bending, simultaneous to the formation of new outer-rise faults or ii) episodic interplate coupling related to the rugged morphology of the faulted downgoing plate. Faults reactivation is concurrent with a local, transient deviatoric stress increase in intraslab domains among these structures. We suggest that slab domains affected by stress increase could be the appropriate location where potential brittle deformation can occur, generating intermediate-depth intraslab earthquakes, that are predominantly localized in heterogeneous regions of dense faulting formed within slab-segments boundaries. The temporal coincidence of stress growth at intermediate depths and throw-growth of, newly-formed, outer-rise faults at the surface may possibly explain the observed global positive correlation of intermediate-depth seismicity rate with maximal fault throw.