Search

Since November 30, 2020, an intense seismic swarm and transient deformation have been continuously observed in the Noto Peninsula, central Japan, which is a non-volcanic/geothermal area far from major plate boundaries. We modeled transient deformation based on a combined analysis of multiple Global Navigation Satellite System (GNSS) observation networks, including one operated by a private sector company (SoftBank Corp.), relocated earthquake hypocenters, and tectonic settings. Our analysis showed a total displacement pattern over two years shows horizontal inflation and uplift of up to ~70 mm around the source of the earthquake swarm. In the first three months, the opening of the sub-horizontal tensile crack had an estimated volumetric increase of ~1.4 x 107 m3 at a depth of ~16 km. Over the next 15 months, the observed deformation was well reproduced by shear-tensile sources, which represent an aseismic reverse-type slip and the opening of a southeast-dipping fault zone at a depth of 14–16 km. We suggest that the upwelling fluid spread subhorizontally at a depth of ~16 km through an existing permeable fault zone and then diffused into the fault zone, triggering a long-lasting sub-meter aseismic slip below the seismogenic depth. The aseismic slip further triggered intense earthquake swarms at the updip.

SUMMARY The Japan forearc plays a crucial role in modulating the post-seismic deformation in response to the enormous stress perturbation induced by the 2011 Tohoku-oki earthquake. Dense geodetic observations across Japan have revealed coupled interactions between afterslip on the subducting plate interface and viscous deformation within the mantle wedge, and detailed numerical models can provide further profound insights into the forearc rheology. Recent studies have revealed the presence of a stagnant section in the forearc mantle of the Tohoku subduction zone, and here we investigate the associated along-arc variation of the stagnant part of the mantle wedge (cold nose) across Japan. We utilize a newly deployed geodetic network along a corridor in the Fukushima–Niigata region and compare the surface deformation pattern to that of the Miyagi–Yamagata corridor close to the main rupture area. We present a 3-D rheological model using laboratory-derived constitutive laws to simulate the geodetic observations including displacement fields and their time-series. Our results suggest along-arc heterogeneity in the forearc mantle rheology; specifically, we find a narrower cold nose in the Miyagi region and a wider one in the Fukushima forearc. The geodetic inferences on the forearc variation are consistent with along-arc spatial heterogeneity in the cut-off depth for shallow earthquakes as well as comparative measurements of the respective geothermal gradients between the Miyagi and Fukushima regions.

Ocean bottom pressure-gauge (OBP) records play an important role in seafloor geodesy, but oceanographic fluctuations in OBP data are a major source of noise in seafloor transient crustal deformation observations, including slow slip events (SSEs), so it is important to evaluate them properly. To extract the significant characteristics of the oceanographic fluctuations, we applied principal component analysis (PCA) to the 3-year Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) OBP time series for 40 stations during 2016–2019. PCA can separate several oceanographic signals based on the characteristics of their spatial distributions, although transient tectonic signals could not be clearly confirmed from the observed pressure records. The higher-order modes of the principal component reflected the oceanographic variation along the sea depth, and we interpreted that they were caused by the strength or weakness and meandering of ocean geostrophic currents, based on a comparison to the global ocean model ECCO2 by “Estimating the Circulation and Climate of the Ocean” (ECCO) consortium. In addition, to evaluate the ability of PCA to separate transient crustal deformation from oceanographic fluctuations, we conducted a synthetic test assuming an SSE by rectangular faults. The assumed synthetic tectonic signal can be separated from the oceanographic signals and included in the principal component independently depending on its amplitude. We proposed a transient event-detection method based on the spatial distribution variation of a specific principal component with or without a tectonic signal. This method can detect transient tectonic signals larger than moment-magnitude scale M 5.9 from OBP records.

OBP (Ocean bottom pressure-gauge) is an essential sensor in crustal deformation observation in the marine region. Still, non-tidal oceanographic fluctuations in OBP data are a significant source of noise in seafloor transient crustal deformation observations, including SSEs (slow slip events), so it is essential to evaluate them properly. To extract and assess the significant characteristics of the oceanographic fluctuations, we applied PCA (principal component analysis) to the DONET (Dense Oceanfloor Network System for Earthquakes and Tsunamis, southwest margin of Japan) OBP time series of 40 stations for three years (2016–2019). PCA could separate several oceanographic signals based on the characteristics of their spatial distributions. The higher-order modes of the PC were distributed in a varying manner with sea depth, and we interpreted that they were caused by the strength and meandering of the ocean geostrophic currents based on similar spatial distribution with the global ocean models. Since PCA cannot detect the significant tectonic signal in observed data, we applied a synthetic ramp simulating SSE to the observation to evaluate the performance of PCA in tectonic signal detection. The assumed synthetic ramp could be separated into an independent principal component according to its amplitude (i.e., the scale of the events). We proposed a detection method of a transient event using the spatial distribution change of the principal component with and without the synthetic ramp using their normalized inner product. Our method was able to detect the tectonic signal of events of MW5.9 or larger from the OBP time series., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Following the 2011 Tohoku Earthquake, we constructed seafloor geodetic benchmarks for GNSS-Acoustic measurement at twenty sites along the Japan trench in September 2012 and have started repeating surveys since then. Reliable horizontal displacement rates were obtained to date for a sufficiently long period of surveys, which revealed the coexistence of viscoelastic relaxation and after slips from place to place. Further analysis to estimate vertical motion, we preliminary exposed regions of uplift and subsidence, although the expected errors were still significant. However, the pattern of vertical motion gives independent information from the horizontal ones for verifying viscoelastic models and evaluating the extent of after slips.We introduced an unmanned autonomous vehicle, called Waveglider (WG), as a surface platform instead of a ship, which overcomes the deficiency in ship-time in the sense of budget and human resources. Actually, data obtained by WG bear comparison with that by shipboard survey, and even the onboard-processed data can be transmitted to the onshore station via satellite system nearly in realtime. Moreover, significantly intensive use of WG helps increase the survey frequency, which can have a chance to identify slow slip events; for instance, marine seismometers have revealed the existence of slow events off the Sanriku region near our survey sites. The WG deficit is sometimes trapped against sea current even along the Japan trench, typically when over 2 knots, and fails into low power conditions depending on weather, season, and solar culmination altitude. Well-organized planning and operation may reduce such deficit. More practically, the slower speed of WG prevents efficient moving survey over a transponder array, especially for deep (>5000m) sites having a large footprint of the array, which is typical for our sites. Insufficient moving survey degrades the accuracy in vertical crustal movement, the importance of which increases to monitor the afterslip distribution as noted above. Then we solve this problem using a different approach that utilizes different incident angles even in point survey by employing two concentric triangles of different sizes for a six transponder site or a triangle with a centered one for a four transponder site.If WG operation would become more common and can be appropriative, a fully continuous survey will be realized at a specific site without a moored buoy. This will be valuable not only for detecting temporal phenomena like slow slip events but also for disaster mitigation to monitor offshore fault failure in realtime. In addition, such prompt measurement just after a large earthquake reveals rapid postseismic deformation in an early stage. Long-term continuous operation requires particular battery specifications and operational fashion for seafloor transponders. We are also designing such transponders at this moment.

A rapid source fault estimation and quantitative assessment of the uncertainty of the estimated model can elucidate the occurrence mechanism of earthquakes and inform disaster damage mitigation. The Bayesian statistical method that addresses the posterior distribution of unknowns using the Markov chain Monte Carlo (MCMC) method is significant for uncertainty assessment. The Metropolis–Hastings method, especially the Random walk Metropolis–Hastings (RWMH), has many applications, including coseismic fault estimation. However, RWMH exhibits a trade-off between the transition distance and the acceptance ratio of parameter transition candidates and requires a long mixing time, particularly in solving high-dimensional problems. This necessitates a more efficient Bayesian method. In this study, we developed a fault estimation algorithm using the Hamiltonian Monte Carlo (HMC) method, which is considered more efficient than the other MCMC method, but its applicability has not been sufficiently validated to estimate the coseismic fault for the first time. HMC can conduct sampling more intelligently with the gradient information of the posterior distribution. We applied our algorithm to the 2016 Kumamoto earthquake (MJMA 7.3), and its sampling converged in 2 × 104 samples, including 1 × 103 burn-in samples. The estimated models satisfactorily accounted for the input data; the variance reduction was approximately 88%, and the estimated fault parameters and event magnitude were consistent with those reported in previous studies. HMC could acquire similar results using only 2% of the RWMH chains. Moreover, the power spectral density (PSD) of each model parameter's Markov chain showed this method exhibited a low correlation with the subsequent sample and a long transition distance between samples. These results indicate HMC has advantages in terms of chain length than RWMH, expecting a more efficient estimation for a high-dimensional problem that requires a long mixing time or a problem using nonlinear Green’s function, which has a large computational cost. Graphical Abstract

Obvious crustal deformation is observed during a postseismic period as well as a coseismic period associated with a large earthquake. Major mechanisms of transient postseismic deformation are known as afterslip and viscoelastic relaxation. Since the viscoelastic relaxation occurs as a response to a coseismic slip, postseismic deformation provides information on coseismic deformation through the viscoelastic response. However, most previous studies have not thoroughly utilized postseismic geodetic observational data for revealing coseismic slip behaviors. In this study, we developed a slip inversion method that simultaneously estimates coseismic slip and postseismic slip distributions from coseismic and postseismic geodetic observational data using viscoelastic Green’s function (viscoelastic inversion method). We investigated the performance of the viscoelastic inversion method via two synthetic tests: one assumed a strike–slip event along an inland fault, while the other assumed a dip–slip event along a plate interface in a subduction zone. Both synthetic tests demonstrated that when extensive postseismic observational data were given, the viscoelastic inversion method provided a superior spatial resolution of coseismic slip distributions compared to conventional elastic inversion distributions. We also applied the viscoelastic inversion method to co- and post-seismic deformations associated with the 2011 Tohoku-oki earthquake. The seafloor geodetic observational network of the off-Tohoku region has been widely extended after the occurrence of the mainshock. Using this extended seafloor geodetic observational data, we successfully improved the spatial resolution of the coseismic slip distribution through the viscoelastic inversion method. Furthermore, using the seafloor observational data during the postseismic period, our inversion method enables us to obtain high spatial resolution of the coseismic slip in the offshore area and a reasonable coseismic slip distribution even if seafloor observational data during the coseismic period are unavailable. These results clarify the importance of deploying a geodetic observational network even after large coseismic events to assess past coseismic slip behaviors by considering the viscoelasticity of the Earth.

In this research area, methodologies for prior predictions of potential hazards and real-time estimations of progressing hazards caused by earthquakes and volcanic eruptions are proved for disaster mitigation. The studies are based on the latest understanding of earthquake processes, volcanic activities, and the crustal structure. The studies have been conducted through the co-operation of the research fields of disaster prevention engineering and social science, in conjunction with the practical services of on-site works, to effectively provide the people with advance and immediately prior predictions. Predicting hazard potentials with high accuracy is important to the planning of disaster countermeasures. The hazards include ground motions, tsunamis, and land slides due to earthquakes as well as flows of volcanic ash and lava from volcanic activities. Real-time estimation of hazards and simultaneous transmission of the estimated results are also help in the mitigation of secondary hazards that followed the main disaster. Typical examples of the results are presented in this review paper.

MCFD2 and ERGIC-53, which are the products of causative genes of combined factor V and factor VIII deficiency, form a cargo receptor complex responsible for intracellular transport of these coagulation factors in the early secretory pathway. In this study, using an NMR technique, we successfully identified an MCFD2-binding segment from factor VIII composed of a 10 amino acid sequence that enhances its secretion. This prompted us to examine possible effects of attaching this sequence to recombinant glycoproteins on their secretion. We found that the secretion level of recombinant erythropoietin was significantly increased simply by tagging it with the passport sequence. Our findings not only provide molecular basis for the intracellular trafficking of coagulation factors and their genetic deficiency but also offer a potentially useful tool for increasing the production yields of recombinant glycoproteins of biopharmaceutical interest., The secretion of blood coagulation factor V and factor VIII (FV and FVIII) are driven by secretion factors ERGIC-53 and MCDF2. Here, the authors report a 10 amino acid motif from FVIII that can enhance secretion of another glycoprotein erythropoietin (EPO).

The Sakurajima volcano is characterized by frequent vulcanian eruptions at the Minamidake or Showa crater in the summit area. We installed an integrated monitoring system for the detection of volcanic ash (composed of remote sensing sensors XMP radars, lidar, and GNSS with different wave lengths) and 13 optical disdrometers on the ground covering all directions from the crater to measure drop size distribution and falling velocity. Campaign sampling of volcanic ash supports the conversion of particle counts measured by the disdrometer to the weight of volcanic ash. Seismometers and tilt/strain sensors were used to estimate the discharge rate of volcanic ash from the vents. XMP radar can detect volcanic ash clouds even under visual difficulty because of weather such as fog or clouds. A vulcanian eruption on November 13 was the largest event at the Sakurajima volcano in 2017; however, the volcanic plume was not visible due to clouds covering the summit. Radar revealed that the volcanic plume reached an elevation of 4.2–6.2 km. Post-fit phase residuals (PPR) from the GNSS analysis increased suddenly after the eruption, and large-PPR paths from the satellites to the ground-based receivers intersected each other at an elevation of 4.2 km. The height of the volcanic plume was also estimated from the discharge rate of volcanic ash to be 4.5 km, which is empirically related to seismic energy and the deflation volume obtained via ground deformation monitoring. Using the PUFF model, the weight of the ash-fall deposit was accurately forecast in the main direction of transport of the volcanic ash, which was verified by disdrometers. For further advances in forecasting of the ash-fall deposit, we must consider high-resolution wind field, shape of volcanic plume as the initial value, and the particle number distribution along the volcanic plume.

Estimating the coseismic slip distribution and interseismic slip-deficit distribution play an important role in understanding the mechanism of massive earthquakes and predicting the resulting damage. It is useful to observe the crustal deformation not only in the land area, but also directly above the seismogenic zone. Therefore, improvements in terms of measurement precision and increase in the number of observation points have been proposed in various forms of seafloor observation. However, there is lack of research on the quantitative evaluation of the estimation accuracy in cases where new crustal deformation observation points are available or when the precision of the observation methods have been improved. On the other hand, the crustal structure models are improving and finite element analysis using these highly detailed crustal structure models is becoming possible. As such, there is the real possibility of performing an inverted slip estimation with high accuracy via numerical experiments. In view of this, in this study, we proposed a method for quantitatively evaluating the improvement in the estimation accuracy of the coseismic slip distribution and the interseismic slip-deficit distribution in cases where new crustal deformation observation points are available or where the precision of the observation methods have been improved. As a demonstration, a quantitative evaluation was performed using an actual crustal structure model and observation point arrangement. For the target area, we selected the Kuril Trench off Tokachi and Nemuro, where M9-class earthquakes have been known to occur in the past and where the next imminent earthquake is anticipated. To appropriately handle the effects of the topography and plate boundary geometry, a highly detailed three-dimensional finite element model was constructed and Green’s functions of crustal deformation were calculated with high accuracy. By performing many inversions via optimization using Green’s functions, we statistically evaluated the effect of increase in the number of observation points of the seafloor crustal deformation measurement and the influence of measurement error, taking into consideration the diversity of measurement errors. As a result, it was demonstrated that the observation of seafloor crustal deformation near the trench axis plays an extremely important role in the estimation performance.

During the 2011 Tohoku-oki earthquake the pacific coast of northeast Japan experienced significant subsidence, while in the years after it has undergone a continuous phase of uplift during the post-seismic period. The dense geodetic network deployed by GEONET and Tohoku university between 2011 and 2016 have captured variations in surface deformation along the coast, highlighting rapid uplift rates of ~7 cm/year on the Miyagi coast (Muto et al., 2019, Sci.Adv.) and ~3-4 cm/year on the Fukushima and Iwate coasts. Previous studies in the last decade have revealed the post-seismic deformation is due to a combination of both rapid viscoelastic flow and stress-driven afterslip, explaining the post-seismic vertical deformation pattern over northeast Japan as well as unravel its associated rheological complexity (e.g., Agata et al., 2019, Nat. Commun; Freed et al., 2017, EPSL; Hu et al., 2016, JGR; Muto et al., 2019, Sci.Adv.). Furthermore, continuous coastal uplift has had societal consequences, where the piers at the port are no longer suited to conduct many activities, particularly those for the fish industry. The large co-seismic subsidence of coastal areas caused the submersion of port piers, with rapid rebuilding to return the now submerged piers to sea-level. Nevertheless, the continuous uplift in the post-seismic period has now raised these rebuild piers above sea level and necessitates reduction in height back to sea level again (Iinuma, 2018, JDR). In this presentation, we employ forward modeling to improve estimates of future uplift and the time required for full recovery of coastal regions to their pre-event relative sea level. We present a numerical model using laboratory-derived constitutive laws and compare our modeled displacement with the geodetic observations (Ozawa et al., 2012, JGR; Tomita et al., 2017, Sci.Adv.; Watanabe et al., 2014, GRL). The model is constrained by terrestrial and seafloor geodetic observations in both horizontal and vertical components and incorporates a three-dimensional heterogeneous viscoelastic rheology fully coupled with stress-driven afterslip on the plate interface. Our model exhibits good agreement with the cumulative displacements, both in magnitude and azimuthal direction. We extend the time-series simulation for a further 20 years and estimate the recovery time to pre-event levels for the GNSS sites along the coastal areas. Our results show a recovery period of ~18 years after the mainshock for Ishinomaki site in Miyagi prefecture, which had the largest coseismic subsidence (up to ~1.2 m). We also estimate a recovery period of ~14-16 years for the coastal areas of Iwate and Fukushima prefectures, which experienced coseismic subsidence of ~0.5 m. The model adds an improvement to the previous estimates (Iinuma, 2018, JDR) by incorporating consideration of the coupling of viscoelastic relaxation and stress-driven afterslip.

Recent studies have shown that ocean-bottom pressure gauges (OBPs) can record seismic waves in addition to tsunamis and seafloor permanent displacements, even if they are installed inside the focal...

We used temporal seismic observation using pop-up type ocean-bottom seismometers to detect a number of low-frequency tremors (LFTs) immediately after the 2011 Tohoku-Oki earthquake in the northern periphery of its aftershock area. The near-field observation clearly distinguished LFTs from regular earthquakes based on their spectral shape in the frequency band of 1–4 Hz. In addition to the LFTs accompanied by known very low frequency earthquakes (VLFEs), more than 130 LFTs without known VLFE activity were detected during April–October, 2011. The newly detected LFTs were in the vicinity of a sequence of small repeating earthquakes indicating mixed distribution of LFTs and regular interplate earthquakes in the region. The LFTs and repeating earthquake activities show a periodicity of 60–100 days, which is similar to that of the LFT activity in the later period (2016–2018). This suggests that the LFT activity is modulated by sustained background aseismic slip events throughout the postseismic period of the 2011 mainshock.

SummaryThe spiral wave is a commonly observed spatio-temporal order in diverse signal relaying systems. Although properties of generated spirals have been well studied, the mechanisms for their spontaneous generation in living systems remain elusive. By the newly developed imaging system for trans-scale observation of the intercellular communication among ∼130,000 cells of social amoeba, we investigated the onset dynamics of cAMP signaling and identified mechanisms for the self-organization of the spiral wave at three distinct scalings: At the population-level, the structured heterogeneity of excitability fragments traveling waves at its high/low boundary, that becomes the generic source of the spiral wave. At the cell-level, both the pacemaking leaders and pulse-amplifying followers regulate the heterogeneous growth of the excitability. At the intermediate-scale, the essence of the spontaneous wave fragmentation is the asymmetric positioning of the pacemakers in the high-excitability territories, whose critical controls are operated by a small number of cells, pulse counts, and pulse amounts.

We have started to develop a next-generation microwave radiometer to be used in millimeter-wave spectroscopy for the high-resolution and high-precision monitoring of water vapor behavior. The new radiometer will be suitable for not only space geodetic techniques such as VLBI and GNSS, but also field measurements to monitor, for example, volcanic activities and cumulonimbus cloud generation. The planned front-end system for our new microwave radiometer has a wide bandwidth feed of 20–60 GHz. A signal from the feed is separated into two linear orthogonal polarized signals using an orthomode transducer (OMT); one is in the 20–30 GHz feed and the other is in the 50–60 GHz feed. We are now planning to cool the wideband feed, OMT, and LNA for each signal at 77 K using a Stirling cryocooler to improve the signal-to-noise ratio. We assembled a room-temperature 20–30 GHz receiver without the cooling system until the middle of 2019 as a first step of our development. We implemented the new receiver into the 3.7 m dish at Okinawa Electromagnetic Technology Center, National Institute of Information and Communications Technology (NICT), and carried out the first measurements using this receiver for validation tests in October 2019. Quick-look data obtained by the new receiver shows good power signals for the expected receiving band of 18–28 GHz. We are now developing another receiver for a higher band of 50–60 GHz, and we are going to implement the second one into the new prototype radiometer by the end of this fiscal year.

The tsunami disasters that occurred in Indonesia, Chile, and Japan have inflicted serious casualties and damaged social infrastructures. Tsunami forecasting systems are thus urgently required worldwide. We have developed a real-time tsunami inundation forecast system that can complete a tsunami inundation and damage forecast for coastal cities at the level of 10-m grid size in less than 20 min. As the tsunami inundation and damage simulation is a vectorizable memory-intensive program, we incorporate NEC's vector supercomputer SX-ACE. In this paper, we present an overview of our system. In addition, we describe an implementation of the program on SX-ACE and evaluate its performance of SX-ACE in comparison with the cases using an Intel Xeon-based system and the K computer. Then, we clarify that the fulfillment of a real-time tsunami inundation forecast system requires a system with high-performance cores connected to the memory subsystem at a high memory bandwidth such as SX-ACE.

cAMP is one of the most important second messengers in biological processes. Cellular dynamics of cAMP have been investigated using a series of fluorescent indicators; however, their sensitivity was sub-optimal for detecting cAMP dynamics at a low concentration range, due to a low ligand affinity and/or poor dynamic range. Seeking an indicator with improved detection sensitivity, we performed insertion screening of circularly permuted mApple, a red fluorescent protein, into the cAMP-binding motif of PKA regulatory subunit Iα and developed an improved cAMP indicator named R-FlincA (Red Fluorescent indicator for cAMP). Its increased affinity (Kd = 0.3 μM) and expanded dynamic range (860% at pH 7.2) allowed the detection of subtle changes in the cellular cAMP dynamics at sub-μM concentrations, which could not be easily observed with existing indicators. Increased detection sensitivity also strengthened the advantages of using R-FlincA as a red fluorescent indicator, as it permits a series of applications, including multi-channel/function imaging of multiple second messengers and combinatorial imaging with photo-manipulation. These results strongly suggest that R-FlincA is a promising tool that accelerates cAMP research by revealing unobserved cAMP dynamics at a low concentration range.

The short period seismometer-based magnitude saturation problem, especially for events with magnitude > 8, can be improved by a real-time Global Navigation Satellite System (GNSS) positioning technique, which has enabled rapid estimation of a finite fault model for a large earthquake without any saturation. A new real-time fault modeling system based on the GNSS Earth Observation Network (GEONET) is developed and is under experimental operation in Japan. In this paper, we present the newly developed system REGARD (the Real-time GEONET Analysis system for Rapid Deformation monitoring), which consists of real-time GNSS positioning, automatic detection of coseismic displacement by the event, and quasi real-time finite fault model inversion routines. The performance of the automatic event detection system is tested through experimental real-time operation based on GEONET data for two months. Furthermore, we also test the reliability of the finite fault model inversion routines using real raw GNSS data observed for past large earthquakes: the 2003 Tokachi-oki earthquake (moment magnitude (Mw) 8.3), the 2011 Tohoku earthquake (Mw 9.0), and the 2011 off Ibaraki earthquake (Mw 7.7). A simulated 1707 Hoei-type Nankai Trough earthquake (Mw 8.7) is also tested. The real-time experimental operation shows that real-time GNSS positioning is precise enough to detect all the tested earthquakes, and the inversion results demonstrate that the REGARD can reliably estimate the earthquake size and its extent within 3 min after the origin time. These results suggest that the REGARD system will complement the seismometer-based magnitude determination system.

We estimated the coseismic slip distribution associated with the Mw 7.2 and 6.5 foreshocks of the 2011 Tohoku-Oki earthquake based on analysis of the tsunami waveform records obtained just above their focal areas. The results show that the main rupture areas of each of the foreshocks do not overlap with each other, and show a distribution that is complementary to the postseismic slip area of the first Mw 7.2 foreshock as well as to the epicenters of smaller earthquakes during foreshock activity. After the second largest foreshock, seismicity increased in the area between the rupture area of the second largest foreshock and the mainshock epicenter, suggesting propagation of aseismic slip towards the mainshock epicenter. The calculated stress drop of the second largest foreshock was smaller than the largest one, implying strength reduction during the postseismic period of the largest foreshock. Based on a comparison of coastal tsunami records, it is suggested that the asperity ruptured in the M 7.0 earthquake in 1981 ruptured again during the largest foreshock in 2011, but it expanded to the updip side of the 1981 rupture area and became larger in magnitude, exemplifying the irregularity of earthquake recurrence in the area.

Genetically encoded indicators driven by the Förster resonance energy transfer (FRET) mechanism are reliable tools for live imaging. While the properties of FRET-based indicators have been improved over the years, they often suffer from a poor dynamic range due to the lack of comprehensive understanding about how to apply an appropriate strategy to optimize the FRET parameters. One of the most successful optimizations is the incorporation of circularly permuted fluorescent proteins (cpFPs). To better understand the effects of this strategy, we systematically investigated the properties of the indicators by utilizing a set of FRET backbones consisting of native or one of the most effective cp variants (cp173FPs) with considerations of their order. As a result, the ordering of donor and acceptor FPs, which has been ignored in previous studies, was found to significantly affect the dynamic range of indicators. By utilizing these backbones, we succeeded in improving a cGMP indicator with 3.6-fold increased dynamic range and in generating an ultrasensitive cAMP indicator capable of environmental imaging, demonstrating the practical importance of the ordering of donors and acceptors in the engineering of FRET-based indicators.

Using two-dimensional finite element modeling, we reproduced the observed postseismic deformation of the 2011 Tohoku-Oki earthquake. Our model, which accounts for the lithosphere-asthenosphere boundary and weak zones beneath volcanoes, was able to reproduce small-scale (

The subduction rate of an oceanic plate may accelerate after large earthquakes rupture the interplate coupling between the oceanic and overriding continental plates. To better understand postseismic deformation processes in an incoming oceanic plate, we directly measured the displacement rate of the Pacific Plate near the Japan Trench after the 2011 Tohoku-Oki earthquake using a GPS/acoustic technique over a period of 2 years (September 2012 to September 2014). The displacement rate was measured to be 18.0 ± 4.5 cm yr−1 (N302.0°E) relative to the North American Plate, which is almost twice as fast as the predicted interseismic plate motion. Because the sum of steady plate motion and viscoelastic response to the Tohoku-Oki earthquake roughly accounts for the observed displacement rate, we conclude that viscoelastic relaxation is the primary mechanism responsible for postseismic deformation of the Pacific Plate and that significant subduction acceleration did not occur at least not during the observation period.

The 2011 Tohoku-Oki earthquake (M9.0) occurred on March 11, 2011. Many studies have investigated the co-seismic slip distribution of the earthquake on the plate interface based on terrestrial seismological and geodetic data and seafloor geodetic data. However, since seafloor stations installed before the main shock were concentrated in the off Miyagi Prefecture area, the spatial extent of the area of very large slip on the shallow plate interface was not well constrained along the direction parallel to the Japan Trench. After the main shock, large post-seismic deformations were detected by the terrestrial Global Navigation Satellite System (GNSS) observation stations and the seafloor station network, which includes 20 new seafloor stations installed after the 2011 Tohoku-Oki earthquake. The post-seismic displacement rate field in the offshore area revealed that the viscoelastic relaxation in the asthenospheric layer beneath the earth's elastic crust is the main cause of the post-seismic deformation not the afterslip on the plate interface. Since stress perturbation due to the co-seismic slip excited the viscoelastic relaxation, the post-seismic displacement rates provide information about the co-seismic slip. Therefore, it is possible to constrain the co-seismic slip distribution on the shallow plate interface near the Japan Trench, based on the post-seismic displacements by applying Green's function, which includes viscoelastic displacement evolution. We simultaneously inverted co- and post-seismic displacement data to estimate the co- and post-seismic slip distributions of the 2011 Tohoku-Oki earthquake with better spatial resolution than models based on the elastic Green's function. The result indicates that the shallow co-seismic rupture extended maximally from 37.0°N to 39.2°N near the Japan Trench. Afterslip distribution was also well constrained in comparison to previous studies because of the introduction of the newly established GNSS-Acoustic observation network.

Lack of observation network in the vicinity of oceanic intraplate earthquake lead the estimation of coseismic fault slip with high uncertainty. Satriano et al. [2] and Wei et al. [3] found NNE trending left-lateral slip as the primary features. In another hand, Yue et al. [4] and Hill et al. [5] proposed WNW trending right-lateral faults structure as the main characteristic. Here, we investigate the coseismic fault model that could explain the coseismic offset both vertical and horizontal in a 3-D heterogeneous earth structure. We constructed finite element model that include three-dimensional velocity structure, topography/bathymetry, spherical-earth and subducting slab. In this study, we employed scaling slip to adjust slip amount and total seismic moment. Instead of original slip amount, we preserve seismic moment as a basis comparison. Based on vertical and horizontal observation data, WNW trending right-lateral fault could fit better than NNE trending left-lateral fault. The present study demonstrates best-fit calculation using scaling slip optimized to the horizontal or vertical observation lead the both fault model worsen the misfit of vertical or horizontal component, respectively. This result analysis indicates a trade-off between vertical and horizontal component and reflects the importance of revisiting the fault slip modeling incorporating vertical and horizontal data equally.Lack of observation network in the vicinity of oceanic intraplate earthquake lead the estimation of coseismic fault slip with high uncertainty. Satriano et al. [2] and Wei et al. [3] found NNE trending left-lateral slip as the primary features. In another hand, Yue et al. [4] and Hill et al. [5] proposed WNW trending right-lateral faults structure as the main characteristic. Here, we investigate the coseismic fault model that could explain the coseismic offset both vertical and horizontal in a 3-D heterogeneous earth structure. We constructed finite element model that include three-dimensional velocity structure, topography/bathymetry, spherical-earth and subducting slab. In this study, we employed scaling slip to adjust slip amount and total seismic moment. Instead of original slip amount, we preserve seismic moment as a basis comparison. Based on vertical and horizontal observation data, WNW trending right-lateral fault could fit better than NNE trending left-lateral fault. The present study demonstrate...