ANCHOR is a novel assimilative model developed at the U.S. Naval Research Laboratory. It extracts ionospheric parameters from RO and ionosonde data and assimilates them as point measurements into the maps of the background parameters using Kalman Filter approach. This paper introduces the ANCHOR algorithm, discusses its coordinate system and background, explains the background covariance formation, discusses the extraction of the ionospheric parameters from the data and the assimilation process, and, finally, shows the results of the observing system simulation experiment.

Black carbon (BC) has several direct, indirect, semi-direct, and microphysical effects on the Earth’s climate system. Analyses of the decade-long measurement of BC aerosols at Varanasi (from 2009 to 2021) was done to understand its impact on radiative balance. General studies suggest that the daily BC mass concentration (mean of 9.18±6.53 µg m–3) ranges from 0.07 to 46.23 µg m–3 and show a strong interannual and intra-annual variation over the 13-year study period. Trend analyses suggest that the interannual variability of BC shows significant decreasing trend (-0.47 µg m–3 yr-1) over the station. The decreasing trend is maximum during the post-monsoon (-1.86 µg m–3 yr-1) and minimum during the pre-monsoon season (-0.31 µg m–3 yr-1). The radiative forcing caused specifically by BC (BC-ARF) at the top of the atmosphere (TOA), surface (SUR), and within the atmosphere (ATM) is found to be 10.3 ± 6.4, -30.1 ± 18.9, and 40.5 ± 25.2 Wm−2, respectively. BC-ARF shows strong interannual variability with a decreasing trend at the TOA (–0.47 Wm–2 yr-1) and ATM ((–1.94 Wm–2 yr-1) forcing, while it showed an increasing trend at the SUR (1.33 Wm–2 yr-1). To identify the potential source sectors and the transport pathways of BC aerosols, concentrated weighted trajectories (CWT) and potential source contribution function (PSCF) analyses have been conducted over the station. These analyses revealed that the primary source of pollution at Varanasi originate from the upper IGP, lower IGP, and central India.

The Chinese Loess Plateau (CLP) in northern China serves one of the most prominent loess records in the world. The CLP is an extensive record of changes in past aeolian dust activity in East Asia; however, the interpretation of the loess records is hampered by ambiguity regarding the origin of loess-forming dust and an incomplete understanding of the circulation forcing dust accumulation. In this study, we used a novel modeling approach combining a dust emission model FLEXDUST with simulated back trajectories from FLEXPART to trace the dust back to where it was emitted. Over 21 years (1999-2019), we modeled back trajectories for fine (~ 2mu) and super-coarse (~ 20mu) dust particles at six CLP sites during the peak dust storm season from March to May. The source receptor relationship from FLEXPART is combined with the dust emission inventory from FLEXDUST to create site-dependent high-resolution maps of the source contribution of deposited dust. The nearby dust-emission areas dominate the source contribution at all sites. Wet deposition is important for dust deposition at all sites, regardless of dust size. Non-negligible amounts of dust from distant emission regions could be wet deposited on the CLP following high-level tropospheric transport, with the super-coarse dust preferentially from emission areas upwind of sloping topography. On an interannual scale, the phase of the Arctic Oscillation (AO) in winter was found to have a strong impact on the deposition rate on the CLP, while the strength of the East Asian Winter Monsoon was less influential.

The paper presents a new method for the decomposition of the horizontal wind divergence among the linear wave solutions on the sphere: inertia-gravity (IG), mixed Rossby-gravity (MRG), Kelvin and Rossby waves. The work is motivated by the need to quantify the vertical velocity and momentum fluxes in the tropics where the distinction between the Rossby and gravity regime, present in the extratropics, becomes obliterated. The new method decomposes divergence and its power spectra as a function of latitude and pressure level. Its application on ERA5 data in August 2018 reveals that the Kelvin and MRG waves made about 6% of the total divergence power in the upper troposphere within 10S-10N, that is about 25% of divergence. Their contribution at individual zonal wavenumbers k can be much larger; for example, Kelvin waves made up to 24% of divergence power at synoptic k in August 2018. The relatively small roles of the Kelvin and MRG waves in tropical divergence power are explained by decomposing their kinetic energies into rotational and divergent parts. The Rossby wave divergence power is 0.3-0.4% at most, implying up to 6% of global divergence due to the beta effect. The remaining divergence is about equipartitioned between the eastward- and westward-propagating IG modes in the upper troposphere, whereas the stratospheric partitioning depends on the background zonal flow. This work is a step towards a unified decomposition of the momentum fluxes that supports the coexistence of different wave species in the tropics in the same frequency and wavenumber bands. 

Understanding the dynamics of sulfur dioxide (SO2) degassing is of primary importance to track temporal variations of volcanic activity. We develop here an algorithm to automatically estimate daily SO2 masses flux from space-borne hyperspectral images (such as those provided by Sentinel-5P/TROPOMI) without requiring prior knowledge of plume direction or speed. The method computes a linear regression, as a function of distance, of SO2 mass integrated in a series of nested circular domains centered on the volcano. An additional term proportional to the square of the distance, depending solely on a cutoff on the minimum reliable pixel column amount, allows for estimating pixel noise and posterior uncertainty. A statistical test is introduced to automatically detect occurrences of volcanic degassing, by comparing estimated flux and its associated uncertainty. After inversion, a single multiplication by plume speed suffices to deduce the SO2 mass flux, without requiring to re-run the inversion. This way, a range of plume speed scenarios can be easily explored. The method is suited for weakly degassing sources or high-latitude volcanoes. It is applied to two case-studies, where temporal correlation between degassing and seismic energy is highlighted: (a) a one-year-long period of intense degassing at Etna, Italy (2021), and (b) a two-years-long period including three eruptions at Piton de la Fournaise, La Réunion (2021–2023). The method is open-source, and is implemented as an interactive tool within the VolcPlume web portal, facilitating near-real-time exploitation of the TROPOMI archive for both volcano monitoring and assessment of volcanogenic atmospheric hazards.

Understanding the formation of the solar system can provide a simplified look at the universe at large. This is because we have a lot of evidence about the formation of our solar system, and because the universe is homogeneous on a large scale. In this paper, we propose a new way for investigating the formation of the Earth and other Solar System objects. Our approach offers insights into details of the formation of the multiple layers within Earth, the existence of water and oil, the variation in mass distribution within Earth, and the origin of mountains, erratic boulders, and moons. According to our proposed approach, Roche Radius can explain the origin of moons, rings and mountains on planets. We have listed and use critical conditions that are required to form celestial objects.

We develop a method to estimate relative seismic moments M0 and corner frequencies fc of acoustic emission events recorded in laboratory experiments from amplitude spectra of signal’s coda composed of reverberated and scattered waves. This approach has several advantages with respect to estimations from direct waves that are often clipped and also are difficult to separate in experiments performed on small samples. Also, inversion of the coda spectra does not require information about the source locations ans mechanisms. We use the developed method to analyze the data of two experiments: (1) on granite from the Voronezh crystal massif and (2) on Berea sandstone. The range of absolute corner frequencies estimated in both experiments is around 70-700 kHz. The range of relative seismic moments covers 103.5. The relation between fc and M0 observed on the first stages of both experiments, consisted of increasing isotropic confining pressure, approximately follow M0 ~ fc-3 scaling and the b-value of the Gutenberg-Richter distribution was found close to 1. This can be interpreted as rupturing of preexisting material defects with a nearly constant stress-drop and has a similarity with observations of ‘natural’ earthquakes. Deviations from this ‘earthquake-like’ behavior observed after applying axial loading and initiation of sample damaging can be interpreted as changes in stress-drop. Lower stress-drops prevail for sandstone and higher for granite sample respectively that can be related to the strength of corresponding material.

To integrate structural subsurface models and smooth seismic velocity models, they need to share common features and resolutions. Here, we propose a new approach for estimating the depth of sudden velocity changes from ambient-noise multi-mode Rayleigh waves applicable to a wide range of frequencies. Approximating the size and shape of the so-called energy ellipse at frequencies where the ellipticity has an extremum allows us to derive the depth of sudden velocity changes as the half height of the energy ellipse. We test our approach theoretically, numerically, and on real data from two geothermal sites by extracting Rayleigh wave ellipticities and phase velocities from three-component beamforming of ambient noise using the python code package B3AMpy. For a small-scale array, our approach validates the depth of quaternary sediments predicted by geological models. For deeper velocity changes, high uncertainties remain but the general trend of inclining boundaries can be recovered well. We demonstrate that, if impedance contrasts are larger than three, our approach is valid for multiple layers, laterally heterogeneous models, and a wide range of Poisson ratios.

Volcanic eruptions generate continuous or episodic tremor, which can provide unique information about activity changes during eruption. However, the wealth of information in episodic tremor patterns is often not harvested and transitions between patterns remain obscure. The 2021 Geldingadalir eruption of the Fagradalsfjall Fires, Iceland, is an exceptional case, where the lava effusion caused continuous tremor, and 8696 tremor episodes spanning two orders of magnitude in duration and repose. Based on seismometer and video camera data, we associate several-minute-long, symmetrical episodes with an open vent system, where lava remains in the crater bowl during repose, connected to a shallow magma compartment. Ramp-shaped episodes, lasting several hours, are associated with a temporary closure of the vent system, where no lava remains in the crater bowl during repose and more time is required to resume effusion. The transition from continuous to episodic effusion is related to the cumulative time spent in effusion and repose, and to external factors like crater wall collapses.

We are developing a new approach to earthquake nowcasting based on science transformers (GC Fox et al., Geohazards, 2022). As explained in the seminal paper by Vaswani et al. (NIPS, 2017), a transformer is a type of deep learning model that learns the context of a set of time series values by means of tracking the relationships in a sequence of data, such as the words in a sentence. Transformers extend deep learning in the adoption of a context-sensitive protocol "attention", which is used to tag important sequences of data, and to identify relationships between those tagged data. Pretrained transformers are the foundational technology that underpins the new AI models ChatGPT (Generative Pretrained Transformers) from openAI.com, and Bard, from Google.com. In our case, we hypothesize that a transformer might be able to learn the sequence of events leading up to a major earthquake. Typically, the data used to train the model is in the billions or larger, so these models, when applied to earthquake problems, need the size of data sets that only long numerical earthquake simulations can provide. In this research, we are developing the Earthquake Generative Pretrained Transformer model, "QuakeGPT", in a similar vein. For simulations, we are using simulation catalogs from the physics-based model Virtual Quake, the statistical model ETAS, and a statistical physics model based on invasion percolation. Observed data, which is the data to anticipate with nowcasting, is taken from the USGS online catalog for California. In this talk, we discuss the architecture of QuakeGPT and report first results. We also report results using other types of simulated seismicity such as slider block models, to quantify how well a Wednesday, 13 December 2023 14:45-14:55 2016-West (Level 2, West, Moscone Center) Nowcasting Earthquakes with QuakeGPT: An AI-Enhanced Earthquak.

The thermochemical structure of the lithosphere controls melting mechanisms in the mantle, as well as the location of volcanism and ore deposits. Obtaining reliable images of the lithosphere structure, and its complex interactions with the asthenosphere, requires the joint inversion of multiple data sets and their associated uncertainties. In particular, the combination of seismic velocity and electrical conductivity, along with proxies for bulk composition and elusive minor phases, represents a crucial step towards fully understanding large-scale lithospheric structure and melting processes. We apply a novel probabilistic approach for joint inversions of 3D magnetotelluric and seismic data to image the lithosphere beneath southeast Australia. The results show a highly heterogeneous lithosphere with deep conductivity anomalies that correlate with the location of Cenozoic volcanism. In regions where the conductivities have been at odds with sub-lithospheric temperatures and seismic velocities, we observe that the joint inversion provides conductivity values consistent with other observations. The results reveal a strong relationship between metasomatized regions in the mantle and i) boundaries of geological provinces, elucidating the subduction-accretion process in the region; ii)distribution of leucitite and basaltic magmatism; iii) independent geochemical data, and iv)a series of lithospheric steps which constitute areas prone to generating small-scale instabilities in the asthenosphere. This scenario suggests that shear-driven upwelling and edge-driven convection are the primary mechanisms for melting in eastern Australia, contrary to the conventional notion of mantle plume activity. Our study presents an integrated lithospheric model for southeastern Australia and provides valuable insight into the mechanisms driving surface geological processes.

Venus boasts an abundance of volcano and volcano-like structures. Synthetic aperture radar images of the surface have revealed extensive evidence of volcanism, including lava flows and edifices. Volcanic activity is further supported by crater statistics, and analysis of topography and gravity data. Unique to Venus, coronae are quasi-circular, volcano-tectonic features exhibiting diverse volcanic characteristics. Despite this, volcanism is often under-represented in formation models. We identify a new subset of coronae that display topographic change subsequent to the emplacement of lava flows within their fracture annuli, pointing to the critical role of volcanism in the formation of these coronae. Through spherical-harmonic distribution analysis, we find that this new subset is spatially related to the full coronae database, pointing to an intrinsic process of coronae formation. Furthermore, coronae exhibit strong correlations and similar spectral shapes at low spherical harmonic degrees with large volcanoes, suggesting a shared geodynamic origin. Our findings underscore the pivotal role of volcanism in coronae formation and highlight the need for future research that integrates magmatic processes into geophysical models.

All instrumented basaltic collapses generate Mw > 5 very long period earthquakes. However, previous studies of source dynamics have been limited to lumped models treating the caldera block as rigid, leaving open questions related to how ruptures initiate and propagate around the ring fault, and the seismic expressions of those rupture dynamics. We present the first 3D numerical model capturing the nucleation and propagation of ring fault rupture, the mechanical coupling to the underlying viscoelastic magma, and the associated seismic wavefield. We demonstrate that seismic radiation, neglected in previous models, acts as a damping mechanism reducing coseismic slip by up to half, with effects most pronounced for large magma chamber volume, high magma compressibility, or large caldera block radius. Viscosity of basaltic magma has negligible effect on collapse dynamics. In contrast, viscosity of silicic magma significantly reduces ring fault slip. We use the model to simulate the 2018 Kīlauea caldera collapse. Three stages of collapse, characterized by ring fault rupture initiation and propagation, deceleration of the downward-moving caldera block and magma column, and post-collapse resonant oscillations, in addition to chamber pressurization, are identified in simulated and observed (unfiltered) near-field seismograms. A detailed comparison of simulated and observed displacement waveforms corresponding to collapse earthquakes with hypocenters at various azimuths of the ring fault reveals a complex nucleation phase for earthquakes initiated on the northwest. Our numerical simulation framework will enhance future efforts to reconcile seismic and geodetic observations of caldera collapse with conceptual models of ring fault and magma chamber dynamics.

Earthquake magnitude is controlled by the rupture area of the fault network hosting the event. For surface-rupturing large strike-slip earthquakes (~MW6+), ruptures must overcome zones of geometrical complexity along fault networks. These zones, or earthquake gates, act as barriers to rupture propagation. We map step-overs, bends, gaps, splays, and strands from the surface ruptures of 31 strike-slip earthquakes, classifying each population into breached and unbreached groups. We develop a statistical model for passing probability as a function of geometry for each group. Step-overs, and single bends are more predictable earthquake gates than double bends and gaps, and ~20% of ruptures terminate on straight segments. Based on our modeled probabilities, we estimate event likelihood as the joint passing probabilities of breached gates and straight segments along a rupture. Event likelihood decreases inversely with rupture length squared. Our findings support a barrier model as a factor in limiting large earthquake size.

In various research fields such as hydrogeology, environmental science and energy engineering, geological formations with fractures are frequently encountered. Accurately characterizing these fractured media is of paramount importance when it comes to tasks that demand precise predictions of liquid flow and the transport of solute and energy within them. Since directly measuring fractured media poses inherent challenges, data assimilation (DA) techniques are typically employed to derive inverse estimates of media properties using observed state variables like hydraulic head, concentration, and temperature. Nonetheless, the considerable difficulties arising from the strong heterogeneity and non-Gaussian nature of fractured media have diminished the effectiveness of existing DA methods. In this study, we formulate a novel DA approach known as PEDL (parameter estimator with deep learning) that harnesses the capabilities of DL to capture nonlinear relationships and extract non-Gaussian features. To evaluate PEDL’s performance, we conduct two numerical case studies with increasing complexity. Our results unequivocally demonstrate that PEDL outperforms three popular DA methods: ensemble smoother with multiple DA (ESMDA), iterative local updating ES (ILUES), and ES with DL-based update (ESDL). Sensitivity analyses confirm PEDL’s validity and adaptability across various ensemble sizes and DL model architectures. Moreover, even in scenarios where structural difference exists between the accurate reference model and the simplified forecast model, PEDL adeptly identifies the primary characteristics of fracture networks.

Coalescence of magnetic flux ropes (MFRs) is suggested as a crucial mechanism for electron acceleration in various astrophysical plasma systems. However, how electrons are being accelerated via MFR coalescence is not fully understood. In this paper, we quantitatively analyze electron acceleration during the coalescence of three MFRs at Earth’s magnetopause using in-situ Magnetospheric Multiscale (MMS) observations. We find that suprathermal electrons are enhanced in the coalescing MFRs than those in the ambient magnetosheath and non-coalescing MFRs. Both first-order Fermi and E|| acceleration were responsible for this electron acceleration, while the overall effect of betatron mechanism decelerated the electrons. The most intense Fermi acceleration was observed in the trailing part of the middle MFR, while E|| acceleration occurred primarily at the reconnection sites between the coalescing MFRs. For non-coalescing MFRs, the dominant acceleration mechanism is the E|| acceleration. Our results further consolidate the important role of MFR coalescence in electron acceleration in space plasma.

Ultra-low velocity zones (ULVZs) above the core-mantle boundary (CMB) are significant structures that connect the lowermost mantle and outer core. As “thin patches” of dramatically low seismic-wave velocity, they are occasionally found near the base of mantle plumes and in-or-near high seismic-wave speed regions above the CMB. The causes of their morphological distribution and geodynamics remain unclear, and simulation results of high-density melts diverge from seismic observations. We introduced a two-dimensional time-dependent Stokes two-phase flow (with melt migration) numerical model to investigate the formation and morphological characteristics of ULVZs caused by CMB-mantle tangential flows and a neighboring cold source (subducted plate). We discovered that (a) the participation of cold sources with temperature differences between ~4000 K at the plume central regions to <~3900 K at the plume-cooling mantle region, separated by horizontal distances of approximately 100 (±<50) km are necessary for the stable existence of dense melts with mass-density difference >+1–2% (even +10%) with respect to the surrounding mantle; additionally, (b) an enhanced tangential flow coincident with the internal reverse circulation within the broad plume base (with speeds >3 times the lowermost-mantle characteristic flow speed) are necessary for higher aspect-ratio-morphology lenses compatible with seismic observations. The CMB-mantle tangential flow and/or outer-core interacting with CMB-topography may help generate mega-ULVZs, particularly if they appear along the edges of large low-shear-wave-velocity provinces (LLSVPs) and in/near high seismic-speed “cold” zones. Thus, we infer that a strong link exists between ULVZ morphology and the dynamic environment of the lowermost mantle and uppermost outer core.

A document by Oumeng Zhang. Click on the document to view its contents.

Microfluidic devices with open lattice structures, equivalent to a type of porous media, allow for the manipulation of fluid transport processes while having distinct structural, mechanical, and thermal properties. However, a fundamental understanding of the design principles for the solid structure in order to achieve consistent and desired flow patterns remains a challenge, preventing its further development and wider applications. Here, through quantitative and mechanistic analyses of the behavior of multi-phase phenomena that involve gas-liquid-solid interfaces, we present a design framework for a new class of microfluidic devices containing porous architectures (referred to as poroFluidics) for deterministic control of multi-phase fluid transport processes. We show that the essential properties of the fluids and solid, including viscosity, interfacial tension, wettability, as well as solid manufacture resolution, can be incorporated into the design to achieve consistent flow in porous media, where the desired spatial and temporal fluid invasion sequence can be realized. Experiments and numerical simulations reveal that different preferential flow pathways can be controlled by solid geometry, flow conditions, or fluid/solid properties. Our design framework enables precise, multifunctional, and dynamic control of multi-phase transport within engineered porous media, unlocking new avenues for developing cost-effective, programmable microfluidic devices for manipulating multi-phase flows. 

The Cenozoic evolution of the Himalaya-Tibet Plateau, dictated by the India-Asia convergence, remains a subject of substantial ambiguity. Here, a thermo-mechanical model is used to show the critical controls of decelerating convergence on the formation and stabilization of distinctive tectonic structures during prolonged collision. At high constant convergence rates, similar to the late Paleogene India-Asia motions, the lower plate crust is injected beneath the overriding crust, uplifting a plateau, first, then is exhumed towards the orogeny front. Conversely, low constant convergence rates, similar to the Neogene India-Asia motions, induce crustal thickening and plateau formation without underplating or exhumation of incoming crust. Strikingly, models simulating the decelerating India-Asia convergence history portray a dynamic evolution, highlighting the transitory nature of features under decreasing convergence, as the orogen shifts to a new equilibrium. In the transitional phase, the slowing of convergence decreases basal shearing and compression, leading to extension and heating in the orogen interiors. This allows diapiric ascent of buried crust and plateau collapse, as accretion migrates to a frontal fold-and-thrust belt. The models provide insights into the multi-stage evolution of the long-lived Himalayan-Tibetan orogeny, from fast early growth of the Tibetan Plateau, through its transient destabilisation and late-stage internal extension, behind the expanding Himalayan belt.

In this study, we examined the peculiarity in the propagation patterns of Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) immediately preceding earthquakes with a magnitude exceeding 6, occurring between 2019 and 2021. We conducted observations of the ionosphere utilizing TEC (Total Electron Content) data obtained from the geostationary satellite QZSS-3. Our findings revealed a significant deceleration in MSTID velocity near the epicentral region approximately one hour before the Yamagata earthquake on June 18, 2019. Similarly, an inversion in the propagation of small-scale TID was documented in the vicinity of the epicenter roughly one hour before the nearshore seismic occurrence off Tanegashima on January 8, 2019. These results share common characteristics with MSTID propagation deceleration and changes in velocity observed before the Kumamoto earthquake in 2016, suggesting that they may assist in characterizing ionospheric precursory phenomena related to earthquakes. This research contributes to a better understanding of the ionospheric response to seismic events and their potential utility as earthquake precursors.

The first-order configuration of the Himalayan orogen is defined by the northward motion of the Indian Plate, whether directly "underplating" under the Tibetan crust or "subducting" beneath a mantle wedge. Our 3D S-wave receiver-functions newly reveal orogen-perpendicular tearing or warping of the Indian Plate. West of 90°E, the southern limit of the Tibetan lithosphere-asthenosphere boundary is at the Indian crustal front, ~100-km north of the Yarlung-Zangbo suture, implying an underplating of the intact Indian lithosphere beneath Tibet. Further east, the delaminated Indian lithospheric mantle during its gravitationally-induced rollback is separated from the Indian crust by an interposed asthenospheric wedge. The nascent Tibetan lithosphere and its subjacent thin asthenosphere continue ~100 km south of the Yarlung-Zangbo suture. This contrast in lithospheric structures across the Yadong-Gulu and Cona-Sangri rifts at 90-92°E, in 2 agreement with helium isotopic anomalies and deep seismicity, requires the subducting Indian Plate be warped or torn.

Dipolarizing flux bundles (DFBs) have been suggested to transport energy and momentum from regions of reconnection in the magnetotail to the high latitude ionosphere, where they can generate localized ionospheric currents that can produce large nighttime geomagnetic disturbances (GMDs). In this study we identified DFBs observed in the midnight sector from ~7 to ~10 RE by THEMIS A, D, and E during days in 2015-2017 whose northern hemisphere magnetic footpoints mapped to regions near Hudson Bay, Canada, and have compared them to GMDs observed by ground magnetometers. We found six days during which one or more of these DFBs coincided within ± 3 min with ≥ 6 nT/s GMDs observed by latitudinally closely spaced ground-based magnetometers located near those footpoints. Spherical elementary current systems (SECS) maps and all-sky imager data provided further characterization of two events, showing short-lived localized intense upward currents, auroral intensifications and/or streamers, and vortical perturbations of a westward electrojet. On all but one of these days the coincident DFB – GMD pairs occurred during intervals of high-speed solar wind streams but low values of SYM/H. In some events, in which the DFBs were observed closer to Earth and with lower Earthward velocities, the GMDs occurred slightly earlier than the DFBs, suggesting that braking had begun before the time of the DFB observation. This study is the first to connect spacecraft observations of DFBs in the magnetotail to intense (>6 nT/s) GMDs on the ground, and the results suggest DFBs could be an important driver of GICs.

We investigated the effects of the propagation path and site amplification of shallow tremors along the Nankai Trough. Using far-field S-wave propagation from intraslab earthquake data, the amplification factors at the DONET stations were 5–40 times against an inland outcrop rock site. Thick (~5 km) sedimentary layers with VS of 0.6–2 km/s beneath DONET stations have been confirmed by seismological studies. To investigate the effects of thick sedimentary layers, we synthesized seismograms of shallow tremors and intraslab earthquakes at seafloor stations. The ratios of the maximum amplitudes from the synthetic intraslab seismograms between models with and without thick sedimentary layers were 1–2. This means that the estimated large amplifications are primarily controlled by thin lower-velocity (< 0.6 km/s) sediments just below the stations. Conversely, at near-source (≤ 20 km) distances, 1-order amplifications of seismic energies for a shallow tremor source can occur due to thick sedimentary layers. Multiple S-wave reflections between the seafloor and plate interface are contaminated in tremor envelopes; consequently, seismic energy and duration are overestimated. If a shallow tremor occurs within underthrust sediments, the overestimation becomes stronger because of the invalid rigidity assumptions around the source region. After 1-order corrections of seismic energies of shallow tremors along the Nankai Trough, the scaled energies of seismic slow earthquakes were 10-10–10-9 irrespective of the region and source depth. Hence, the physical mechanisms governing seismic slow earthquakes can be the same, irrespective of the region and source depth.