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The 2011 Tohoku earthquake was observed by dense strong motion, teleseismic, geodetic, and tsunami networks. We first inverted each of the datasets obtained by the networks separately, for the rupture process of the earthquake. We then performed checkerboard resolution tests for assessing the resolving power of these datasets. In order to overcome the limited resolutions of the separate inversions and differences in their results, we performed a quadruple joint inversion of all these data to determine a source model most suitable for explaining all the datasets. In the obtained source model, the maximum coseismic slip was approximately 35 m, and the total seismic moment was calculated to be 4.2 × 1022 Nm, which yielded Mw = 9.0. The main rupture propagated not only in the strike direction but also in the dip direction and included both the deep area called the Miyagi‐oki region and the compact shallow area near the Japan Trench. Key Points We made the source model reflecting all aspects of the 2011 Tohoku earthquake We performed joint inversion of seismic, geodetic, and tsunami datasets The main rupture included both deep Miyagi‐oki area and compact shallow area

The production of biobutanol from lignocellulosic biomass is a promising route toward sustainable biofuels, but current research is limited due to the use of commercial simulation tools, incomplete process modeling, and insufficient variation in available feedstock. The current work addresses these gaps by developing and evaluating a complete process simulation for biobutanol production using the open-source software DWSIM. A process flow diagram was established based on a comprehensive literature review, and relevant experimental data were collected to guide simulation inputs and validate results. Six process configurations were developed, using dilute acid and autohydrolysis as pretreatment methods, and assessed based on parameters such as feedstock composition, conversion efficiency, and enzymatic hydrolysis performance. Simulation results show that DWSIM effectively models key stages of biobutanol production and accommodates variations in pretreatment and hydrolysis conditions. Processing solid fractions of pretreated biomass yields higher biobutanol concentrations than using liquid prehydrolysate alone, and the efficiency of enzymatic hydrolysis strongly influences the final output. This work demonstrates that DWSIM is a viable platform for simulating biofuel processes and offers a flexible, cost-effective alternative for early-stage process development, followed by process design with implications for future biorefinery integration and technology scaling.

Rupture propagation is controlled by the energy balance between the energy release rate and fracture energy, which varies according to the rupture mode. Although previous studies have primarily investigated rupture modes for entire ruptures, this study focused on the rupture mode during rupture propagation at each spatiotemporal point. Specifically, we introduced a metric to evaluate the rupture propagation direction and compared it with the slip direction. First, the validity of the metric was tested using a synthetic rupture. As a result, the estimated rupture mode for the circular-front rupture was mostly consistent with the assumed rupture mode, although a small slip around the reference location tended to cause a larger difference. We then applied this metric to the real earthquake and obtained various distributions of the spatiotemporal rupture modes. Through the stochastic analysis considering the uncertainty, we confirmed that rupture propagation exhibited a slight directional preference regarding the rupture mode except for the 2008 Iwate Miyagi Inland earthquake. For the 2008 Iwate Miyagi Inland earthquake, a strong barrier zone derived from a fault bending was likely to mitigate the rupture propagation, causing the biased rupture mode preference. This new metric for evaluating the rupture propagation direction can quantitatively represent the effects of rupture attenuation during source processes. Graphical Abstract

Volcano-tectonic earthquake swarms associated with the intrusion of volcanic fluids have been occurring intermittently off the east coast of the Izu Peninsula, Japan. In this study, we estimated the source processes of the six largest earthquakes (Mw 3.9–5.6) that occurred in this region in 2006 and 2009 and investigated their characteristics with respect to areas of swarm activities. We first selected waveforms of smaller earthquakes (Mw3.4–3.9) as empirical Green’s functions and carried out the waveform inversion with 200 time windows for two horizontal components of 10-s-long K-net waveforms. Individual time windows had a duration of 0.2 s and a spacing of 0.05 s. We fixed the total seismic moments to those determined by the National Research Institute for Earth Science and Disaster Resilience of Japan (NIED) and investigated the temporal characteristics of the moment rate functions. We found that two out of the six earthquakes had complex rupture characteristics and that those events took place in an area that had been inactive in terms of swarms for a couple of decades, suggesting that the complexity of these earthquake ruptures was controlled by the maturity of the fractures formed as a result of swarm activities in the region. Graphical Abstract

The complexity of the seismicity pattern for the subduction zone along the oceanic plate triggered the outer rise events and revealed cyclic tectonic deformation conditions along the plate subduction zones. The outer rise earthquakes have been observed along the Sunda arc, following the estimated rupture area of the 2005 MW8.6 Nias earthquakes. Here, we used kinematic waveform inversion (KIWI) to obtain the source parameters of the 14 May 2021 MW6.6 event off the west coast of northern Sumatra and to define the fault plane that triggered this outer rise event. The KIWI algorithm allows two types of seismic source to be configured: the moment tensor model to describe the type of shear with six moment tensor components and the Eikonal model for the rupture of pure double-couple sources. This method was chosen for its flexibility to be applied for different sources of seismicity and also for the automated full-moment tensor solution with real-time monitoring. We used full waveform traces from 8 broadband seismic stations within1000km epicentral distances sourced from the Incorporated Research Institutions for Seismology (IRIS-IDA) and Geofon GFZ seismic record databases. The initial origin time and hypocenter values are obtained from the IRIS-IDA. The synthetic seismograms used in the inversion process are based on the existing regional green function database model and were accessed from the KIWI Tools Green's Function Database. The obtained scalar seismic moment value is 1.18×1019 N·m, equivalent to a moment magnitude MW6.6. The source parameters are 140°, 44°, and −99° for the strike, dip, and rake values at a centroid depth of 10.2 km, indicating that this event is a normal fault earthquake that occurred in the outer rise area. The outer rise events with normal faults typically occur at the shallow part of the plate, with nodal-plane dips predominantly in the range of 30°–60° on the weak oceanic lithosphere due to hydrothermal alteration. The stress regime around the plate subduction zone varies both temporally and spatially due to the cyclic influences of megathrust earthquakes. Tensional outer rise earthquakes tend to occur after the megathrust events. The relative timing of these events is not known due to the viscous relaxation of the down going slab and poroelastic response in the trench slope region. The occurrence of the 14 May 2021 earthquake shows the seismicity in the outer rise region in the strongly coupled Sunda arc subduction zone due to elastic bending stress within the duration of the seismic cycle.

We perform a back projection method to image the rupture propagation and short‐period energy release of the 2012 Off Northern Sumatra earthquake (Mw8.6) using Hi‐net data recorded in Japan. The results show a complex pattern of four conjugate faults over about 180 sec. There is a striking correspondence between the lengths and orientations of our rupture pattern with the distribution of aftershocks. Each of the first three stages of the rupture corresponds to a clear lineation in the aftershocks, with lengths of 200 to 400 km. Rupture speeds for several of the fault segments were very high, about 5 km/s, and exceed the local S‐wave velocity. This is the first example of an oceanic earthquake with supershear rupture speed. Key Points This is one of the most complicated earthquakes, with 4 separate faults The rupture speed is faster than local S‐wave velocity Some oceanic events with fast speeds may have been overlooked in the past

The Noto Peninsula, extending northward into the Sea of Japan, features a narrow, elongated shape, complex coastal topography, and numerous active faults along its coastline. Since December 2020, intense earthquake swarms accompanied by crustal deformation have occurred in the northeastern peninsula, likely caused by fluid upwelling from deep underground. The largest event, a Magnitude 7.6 earthquake, struck on January 1, 2024, with aftershock distributions indicating multiple faults ruptured over approximately 150 km. This study aimed to clarify the temporal and spatial variation in seismic wave radiation and investigate the source process of the M7.6 event using the back-projection method. This method estimates the origin of wave packets recorded by a seismic array. In Japan, seismic networks operated by local governments often include densely distributed stations to evaluate seismic intensity. We used these dense sites as a seismic array complemented by strong ground motion data from NIED K-NET and KiK-net. The analysis assumed three fault planes, based on previous studies. Velocity waveforms in two frequency bands (0.05–2.0 Hz and 0.5–5.0 Hz) were used to estimate areas of strong radiation intensity, representing the sources of seismic waves. In the low-frequency band, strong radiation intensity was observed near the rupture initiation point and in shallow regions of the northern Noto Peninsula, corresponding to large fault slips that caused the uplift of the coastline. In contrast, no strong radiation intensity was detected off the northeast coast of the Noto Peninsula in the low-frequency band, suggesting the absence of a significant slip. High-frequency analysis revealed distributions of strong radiation intensities complementary to those in the low-frequency band. A subevent occurring around 20 s after the rupture initiation was found to originate near the northern coast of the Noto Peninsula. Graphical Abstract

Massive slope failures often occur along the Himalayan orogenic belt, where the Indian plate subducts beneath the Eurasian plate. On March 22, 2021, a slope failure hazard occurred at the Grand Canyon section of the Yarlung Tsangpo River, eastern Himalayan syntaxis, and blocked the river leading to a water level rise of over 10 m. We conducted an analysis of the seismic waveforms recorded by broadband seismic stations which we deployed around the Grand Canyon. These seismograms showed emergent onsets with a total duration of approximately 300 s and corroborated their origination as a glacier collapse along the remote Sedongpu basin. Based on direct measurements of seismic energy and an empirical distance attenuation function, we estimated the volume to be approximately 50 × 106 m3. The source process was interpreted as a single force with three possible stages: progressive coherent block fracturing, mass flow through the Sedongpu basin with downslope acceleration-deceleration-stable motions, and continuous flow along the river after the formation of a temporary dam at the outlet basin.

This study collected and compiled statistical data on atmospheric pollution in Jilin City, China during 2013–2014, using models and methods to calculate the source proportion of PM 2.5 emitted by various sources. The statistical activity levels and emission factors of various pollution sources were found to be key parameters for obtaining the total amount of PM 2.5 in the exhaust gas emitted from all types of pollution sources using an emissions model. In this study, relevant data were collected by the top-down method, and pollutant emission was calculated by the emission factor method to establish the PM 2.5 pollution emission inventory of Jilin City. The source apportionment was calculated using the Chemical Mass Balance (CMB) model. Industrial process source and fixed combustion source are the largest sources of PM 2.5 emission from all sources, respectively. Among the two calculation results, the results of pollution emission inventory are more accurate. The PM 2.5 emission inventory in Jilin was established and countermeasures were proposed focused on the coordinated control of air pollution and the prevention and control of industrial dust pollution sources, as well as environmental management and impact assessment.

Earthquake stress drop Δσ is related to fault slip via Δσ=C⋅μ⋅DLc${\\Delta }\\sigma =C\\cdot \\mu \\cdot \\frac{D}{{L}_{c}}$ , where μ, D, and Lc denote shear modulus, average slip, and fault dimension. C is controlled by the system geometry, characterizes the effective stiffness of the system, and is commonly assumed to be a constant near 1. We use 3D elastostatic models to systematically investigate how C is controlled by fault burial depth, dip angle, and slip direction. We find that C decreases with smaller burial depth and dip angle, with a value for a shallow‐dipping surface‐rupturing fault roughly one‐fifth that of the deeply buried case. Our results help explain the apparent magnitude‐dependent stress drops of megathrust earthquakes in Thingbaijam et al. (2017), https://doi.org/10.1785/0120150291. There may also be implications for the apparent depth‐ and magnitude‐dependence in other source parameters, and for reducing uncertainties in the seismic and tsunami hazard assessments of megathrust earthquakes. Plain Language Summary Characterizing earthquake stress drops is important for both understanding earthquake processes as well as assessing seismic hazards. Estimating stress drops for earthquakes often involves a non‐dimensional parameter C, which characterizes the effective elastic stiffness of the faulting system. In this study, we investigate how interactions between the Earth's surface and the fault affect the theoretical C value, which has not been systematically studied. We find that C decreases with a smaller earthquake depth, and its depth‐dependence exceeds the general “rule of thumb.” Seismological studies for stress drop commonly assume C is a constant. With the SRCMOD earthquake source model catalog (Mai & Thingbaijam, 2014, https://doi.org/10.1785/0119990126; Thingbaijam et al., 2017, https://doi.org/10.1785/0120150291), we show that it is necessary to consider the depth‐dependence of C when measuring stress drops for large earthquakes; otherwise, with a “constant C” assumption, the estimated stress drops would appear to be magnitude‐dependent. Since C factor plays an important role in many theories that relate earthquake sources to their ground motion, our results here may help improve our current seismic and tsunami hazard assessments. Key Points We conduct numerical experiments to investigate the variation of proportionality between earthquake stress drop and slip The proportionality factor C between stress drop and slip is low for a shallow‐buried fault with a small dip angle The systematic variation in C can be significant enough to affect the source parameter analyses that assume a constant C