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Slow slip events (SSEs) are important for the slip budget along a megathrust fault. Although the recurrence of weeks‐long short‐term SSEs (S‐SSEs) in southcentral Alaska has been suggested, a large amount of noise prevented us from detecting discrete events. We applied a systematic detection method to Global Navigation Satellite System data and detected 31 S‐SSEs during the 14‐year analysis period. The events mainly occurred at a depth from 35 to 45 km at a down‐dip extension of the 1964 Alaska earthquake, and the active clusters correlated with the region of the subducting Yakutat microplate. A large cumulative slip of S‐SSEs indicated a significant contribution to stress transfer along the plate interface, and its source area spatially coincided with that of the long‐term SSEs and the afterslip of the 1964 earthquake. Large and recurrent S‐SSEs are key phenomena for understanding interplate slip kinematics in this region. Plain Language Summary: Slow and transient fault slips, called slow slip events (SSEs), are important phenomena accommodating plate motion during interseismic periods. However, detecting SSEs, especially short‐term SSEs (S‐SSEs) that last from days to weeks, is sometimes difficult because of their weak signals. In southcentral Alaska, previous studies have detected S‐SSEs as several discrete events synchronizing with tectonic tremors, but their spatiotemporal distribution and the features of their magnitude and duration are still unclear. We applied a systematic detection method to 14 years of daily Global Navigation Satellite System position data and successfully detected 31 S‐SSEs. We found two major groups of S‐SSEs (S‐SSE clusters) at a depth from 35 to 45 km, which corresponds to a deeper extension of the source of the 1964 Alaska earthquake. These clusters are located in the region where the Yakutat microplate subducts. Maximum cumulative slip reaches 0.27 and 0.43 m in the western and eastern clusters, respectively, and it suggests that S‐SSEs contribute to the reduction of the large amount of interplate slip in their source areas. Key Points: Systematic detection identified 31 short‐term slow slip events in southcentral Alaska from 14 years of Global Navigation Satellite System dataThe slow slips were located at a depth from 35 to 45 km, particularly in the region where the Yakutat microplate subductsThe short‐term slow slips overlap the source areas of the long‐term slow slips and the 1964 Alaska earthquake afterslip [ABSTRACT FROM AUTHOR]

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 2 years shows horizontal inflation and uplift of up to ~ 70 mm around the source of the earthquake swarm. In the first 3 months, the opening of the shallow-dipping tensile crack had an estimated volumetric increase of ~ 1.4 × 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 at a depth of ~ 16 km through an existing shallow-dipping 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. [ABSTRACT FROM AUTHOR]

Slow earthquakes are episodic slow fault slips. They form a fundamental component of interplate deformation processes, along with fast, regular earthquakes. Recent seismological and geodetic observations have revealed detailed slow earthquake activity along the Japan Trench—the subduction zone where the March 11, 2011, moment magnitude (Mw) 9.0 Tohoku-Oki earthquake occurred. In this paper, we review observational, experimental, and simulation studies on slow earthquakes along the Japan Trench and their research history. By compiling the observations of slow earthquakes (e.g., tectonic tremors, very-low-frequency earthquakes, and slow slip events) and related fault slip phenomena (e.g., small repeating earthquakes, earthquake swarms, and foreshocks of large interplate earthquakes), we present an integrated slow earthquake distribution along the Japan Trench. Slow and megathrust earthquakes are spatially complementary in distribution, and slow earthquakes sometimes trigger fast earthquakes in their vicinities. An approximately 200-km-long along-strike gap of seismic slow earthquakes (i.e., tectonic tremors and very-low-frequency earthquakes) corresponds with the huge interplate locked zone of the central Japan Trench. The Mw 9.0 Tohoku-Oki earthquake ruptured this locked zone, but the rupture terminated without propagating deep into the slow-earthquake-genic regions in the northern and southern Japan Trench. Slow earthquakes are involved in both the rupture initiation and termination processes of megathrust earthquakes in the Japan Trench. We then compared the integrated slow earthquake distribution with the crustal structure of the Japan Trench (e.g., interplate sedimentary units, subducting seamounts, petit-spot volcanoes, horst and graben structures, residual gravity, seismic velocity structure, and plate boundary reflection intensity) and described the geological environment of the slow-earthquake-genic regions (e.g., water sources, pressure–temperature conditions, and metamorphism). The integrated slow earthquake distribution enabled us to comprehensively discuss the role of slow earthquakes in the occurrence process of the Tohoku-Oki earthquake. The correspondences of the slow earthquake distribution with the crustal structure and geological environment provide insights into the slow-earthquake-genesis in the Japan Trench and imply that highly overpressured fluids are key to understanding the complex slow earthquake distribution. Furthermore, we propose that detailed monitoring of slow earthquake activity can improve the forecasts of interplate seismicity along the Japan Trench. [ABSTRACT FROM AUTHOR]

In this study, we developed a regional likelihood model for crustal earthquakes using geodetic strain-rate data from southwest Japan. First, the smoothed strain-rate distributions were estimated from continuous Global Navigation Satellite System (GNSS) measurements. Second, we removed the elastic strain rate attributed to interplate coupling on the subducting plate boundary, including the observed strain rate, under the assumption that it is not attributed to permanent loading on crustal faults. We then converted the geodetic strain rates to seismic moment rates and calculated the 30-year probability for M ≥ 6 earthquakes in 0.2 × 0.2° cells, using a truncated Gutenberg–Richter law and time-independent Poisson process. Likelihood models developed using different conversion equations, seismogenic thicknesses, and rigidities were validated using the epicenters and moment distribution of historical earthquakes. The average seismic moment rate of crustal earthquakes recorded during 1586–2020 was only 13–20% of the seismic moment rate converted from the geodetic data, which suggests that the observed geodetic strain rate includes considerable inelastic strain. Therefore, we introduced an empirical coefficient to calibrate the moment rate converted from geodetic data with the moment rate of the earthquakes. Several statistical scores and the Molchan diagram showed all models could predict real earthquakes better than the reference model, in which earthquakes occur uniformly in space. Models using principal horizontal strain rates exhibited better predictive skill than those using the maximum horizontal shear strain rate. There were no significant differences in predictive skill between uniform and variable distributions for seismogenic thickness and rigidity. The preferred models suggested high 30-year probability in the Niigata–Kobe Tectonic Zone and central Kyushu, exceeding 1% in more than half of the analyzed region. The model predictive skill was also verified by a prospective test using earthquakes recorded during 2010–2020. This study suggests that the proposed forecast model based on geodetic data can improve the regional likelihood model for crustal earthquakes in Japan in combination with other forecast models based on active faults and seismicity. [ABSTRACT FROM AUTHOR]

The southern part of the Ryukyu subduction zone has recorded tsunami events with a recurrence interval of several hundred years. Although their source is controversial, one model suggests that the last 1771 Yaeyama tsunami was caused by a shallow megathrust earthquake with a magnitude of 8. However, the current knowledge on interplate coupling based on recent geodetic data is limited. Here, a time series of Global Navigation Satellite System data from January 2010 to February 2021 was analyzed, including newly installed stations by Kyoto and Kyushu Universities, to obtain the distance changes between stations and vertical secular velocities. The distance changes ranged from 2.4 mm/year in contraction and to 4.7 mm/year in extension, and the vertical velocities exhibited no clear uplift or subsidence, with − 2.4 to 1.1 mm/year. The back slip inversion results indicated a slip deficit of 17–47 mm/year to the south of the Yaeyama Islands. The large slip deficit area is complementarily intervened between the shallower source area of low-frequency earthquakes and the deeper slow slip region, suggesting the spatial heterogeneity of frictional properties along the plate interface. If the large slip deficit area accumulates stress in the same rate since the last 1771 earthquake, it could result in a megathrust event with a moment magnitude greater than 7.5. Because the limited onshore data cannot resolve the slip deficit on the shallow plate interface, seafloor geodetic observations are essential to clarify the detailed spatial distribution of the slip deficit and discuss its earthquake and tsunami potential. [ABSTRACT FROM AUTHOR]

Dense Global Navigation Satellite System (GNSS) observations enable the development of megathrust interseismic locking models for the southern Kurile subduction zone where many great earthquakes have occurred. Inversion of these data assuming uniform elastic Earth has yielded slip deficit rates that are unreasonably high and/or full locking depth that is unreasonably large. Using the finite element method, here we construct a new Kurile locking model that includes interseismic viscoelastic stress relaxation and non‐uniform compliance of the elastic upper plate. Inverting the same geodetic data using the new subduction zone model alleviates the previously seen unreasonable features in inferred megathrust locking state. In the new model, full locking extends to shallower depths than the downdip limit of some large megathrust earthquakes including the 2003 Mw 8.0 Tokachi‐oki earthquake, supporting the notion of the shrinking of the locked area before the earthquakes and/or propagation of seismic rupture into creeping areas as previously predicted by friction or dynamic rupture models. By modeling the effects of a few recent M 8 earthquakes, we show that postseismic transients of recent earthquakes, although second‐order, should be addressed in deriving megathrust locking models. The locking state near the trench cannot be resolved by the land‐based GNSS data regardless of the improved model rheology and structure, although independent observations, such as slow earthquakes, may be used to speculate on the near‐trench locking state in various part of the margin in the absence of seafloor geodetic observations. Key Points: Viscoelastic mantle relaxation and non‐uniform compliance of upper plate are of first order importance to interseismic deformationInvoking relaxation and non‐uniform compliance in geodetic inversion leads to shallower megathrust locking than in previous modelsImproved model structure and rheology do not improve resolution of near‐trench locking state, demonstrating need for seafloor geodesy [ABSTRACT FROM AUTHOR]

Slow slip events (SSEs) along subduction zones play an important role in accommodating relative plate motion. SSEs interplay with large megathrust earthquakes and other slow earthquakes, including low frequency and very low frequency earthquakes. The Kanto and Tokai regions of central Japan host frequent slow and large earthquakes, with significant differences in slip behavior along the subduction zones in the Suruga Trough, Sagami Trough, and Japan Trench. In this study, we conducted a systematic search to estimate the fault models and durations of short‐term SSEs using continuous Global Navigation Satellite System data collected from 1994 to 2020. We detected 176 potential SSEs with moment magnitudes of 5.3–7.0 and durations of 0–80 days from the time series. Along the Sagami Trough, two shallow regions at a depth of 10–20 km host Mw ≥ 6.5 SSEs off of the Boso Peninsula and accommodate most of the relative plate motion aseismically. Some SSEs also occur on the deep plate interface down to ∼50 km without tectonic tremors. Along the Japan Trench, the cumulative slip of the SSEs exhibits a bi‐modal depth distribution to avoid the large slip areas of past megathrust earthquakes at 30–40 km depth. The shallow SSEs are in the same depth range (10–30 km) as tectonic tremors, but are spatially separate from tremors along the trench. The detected SSEs have limited temporal correlations with other slow earthquakes and earthquake swarms, which suggests that many factors control the genesis of slow and regular earthquakes. Key Points: A systematic search using 25 years of Global Navigation Satellite System data detected 176 possible SSEs in central JapanSlow slip events (SSEs) along the Japan Trench are distributed updip and downdip of megathrust earthquakes and spatially complement tremors in the updipSynchronization of SSEs with tectonic tremors, very low frequencies, or seismic swarms is limited in central Japan [ABSTRACT FROM AUTHOR]

On 6 December 2016 at 22:03 UTC, a devastating magnitude 6-class strike-slip earthquake occurred along an unidentified and unmapped fault in Pidie Jaya, northern Sumatra. We analysed the possible fault using continuous Global Positioning System (GPS) observation available in the region. In our investigation, we searched for the fault source parameters of the north- and south-dipping left-lateral faults and the west- and east-dipping right-lateral faults. We identified that the fault responsible for the earthquake was located offshore, with a southwest-northeast direction. We also computed the Coulomb failure stress and compared the result with the distribution of the aftershocks. In this study, we demonstrated that the result of the geological field survey conducted soon after the mainshock was attributed to the secondary effects of ground shaking and near-surface deformation, and not surface faulting. The newly identified offshore fault proposed by this study calls for further investigation of the corresponding submarine morphological attributes in this particular region. [ABSTRACT FROM AUTHOR]

Preseismic, coseismic, and 7.5 years of postseismic deformation of the 2003 Mw 8.0 Tokachi‐oki earthquake are modeled using land Global Navigation Satellite System (GNSS) data and two ocean bottom pressure gauges (OBP) using viscoelastic Green's functions. The postseismic slip distribution is shown to not overlap with the main shock or the source regions of past large earthquakes along the southern part of the Kurile trench. The preseismic locking is estimated in the coseismic and postseismic slip regions using the same plate interface geometry. The temporal evolution of the postseismic slip is described with a single logarithmic function. The slip is shown to decay faster updip of the coseismic slip region compared to the downdip extension. Sustained postseismic slip indicates that the interplate locking in the postseismic slip region had not fully recovered to the pre‐2003 status in the 7.5 year analyzed period. Postseismic slip history also indicates rapid recovery of locking in the coseismic slip region. We examined the constraint of the OBP time series for the postseismic deformation modeling and found that the observed uplift at the OBP sites requires small postseismic slip near the trench, where a tsunamigenic M9 earthquake occurred in the seventeenth century. Uplift at the OBP sites does not constrain the absolute slip magnitude between the updip and downdip sides of the OBP sites but requires the slip in the updip side to be smaller than that in the downdip side. Our model describes transient postseismic deformation observed by both land GNSS and OBP. Key Points: Spatiotemporal postseismic slip of the 2003 Tokachi‐oki earthquake for ~7.5 years is estimated using land and seafloor geodetic dataInterplate locking of postseismic slip region had not fully recovered to the pre‐2003 status after 7.5 years following the main shockPostseismic deformation could be responsible for transient seafloor pressure changes following the 2003 event [ABSTRACT FROM AUTHOR]

We analyze Global Navigation Satellite System (GNSS), Interferometric Synthetic Aperture Radar, and accelerometer data within the San‐in Shear Zone in order to clarify the coseismic and postseismic slip distributions associated with the Mw6.2 2016 Central Tottori earthquake. Inversion of the coseismic displacement data to estimate the slip distribution on the rupture fault shows a patch of large slip to the northwest of the hypocenter of the mainshock location. Relocated aftershocks and off‐fault seismicity 1 month after the mainshock are in agreement with stress change patterns caused by the mainshock fault. Inversion of near‐field GNSS displacements in 7 months following the earthquake under the assumption of afterslip does not show a preferred slip patch but rather a smooth distribution of the slip at shallow depths. Restricted slip propagation of afterslip on the 2016 event might suggest that inland faults in the San‐in Shear Zone are immature. Limited resolution of the GNSS data might inhibit us from finding the slip at depth. Key Points: Coseismic and postseismic slip distributions of the 2016 Central Tottori earthquake are retrieved from data inversionCoseismic slip is found northwest of the mainshock hypocenter over an 8‐km × 12‐km area, while afterslip is observed at shallow depthsRestricted slip propagation in the postseismic period suggests immature faults in the San‐in Shear Zone [ABSTRACT FROM AUTHOR]

Seismic activity is associated with crustal stress relaxation, creating inelastic strain in a medium due to faulting. Inelastic strain affects the stress field around a weak body and causes stress concentration around the body, because the body itself has already released stress. Therefore, the understanding of inelastic deformation is important as it generates earthquakes. We investigated average inelastic strain in a spatial bin of Kyushu Island, Japan, and obtained the inelastic strain rate distribution associated with crustal earthquakes, based on the analysis of fault plane solutions and seismic moments. Large inelastic strains (>10 year) were found in the Beppu-Shimabara area, located in the center of Kyushu Island. The strain rate tensor was similar to that of the stress tensor except the absolute value in the area, implying that the inelastic strain was controlled by the stress field. The 2016 Kumamoto earthquake sequence (maximum magnitude 7.3) occurred in the Beppu-Shimabara area, with the major earthquakes located around the high inelastic strain rate area. Inelastic strain in the volume released the stress. In addition, the inelastic strain created an increment of stress around the volume. This indicates that the spatial heterogeneity of inelastic strain might concentrate stress. [ABSTRACT FROM AUTHOR]

We present the initial results of rapid fault estimations for the 2016 Kumamoto earthquake on April 16 ( M 7.3), and coseismic displacements caused by the two large foreshocks that occurred on April 14 ( M 6.5) and April 15 ( M 6.4) from the GEONET real-time analysis system (REGARD), which is based on a Global Navigation Satellite System (GNSS) kinematic positioning technique. The real-time finite-fault estimate ( M 6.85) was obtained within 1 min and converged to M 6.96 within 5 min of the origin time of the mainshock ( M 7.3). The finite-fault estimate shows right-lateral strike-slip fault along the Futagawa fault segment, which is consistent with the finite-fault model inferred from post-processed GNSS and InSAR analysis. Furthermore, significant coseismic displacements were observed due to the April 14 and April 15 foreshocks at nearby sites, though these earthquakes were smaller than the pre-assigned system threshold. Our results also demonstrate the potential for the GNSS-based earthquake early warning system for inland earthquakes. [ABSTRACT FROM AUTHOR]

The global positioning system (GPS) is one of the most powerful tools available for observation of Earth's surface deformation. In particular, coseismic, postseismic, slow transient, and interseismic deformation have all been observed globally by GPS over the past two decades, especially in subduction zones. Moreover, GPS-acoustic techniques have been developed for practical use in the past decade, allowing observation of offshore deformation immediately above slip regions. Here, we describe the application of GPS and GPS-acoustic observations to the detection of deformation due to plate boundary slip for interplate earthquakes as well as afterslip and slow slip events in subduction zones around Japan, where geodetic data coverage is particularly dense. The data demonstrate temporally variable strain accumulation in the source region of the 2011 Mw 9.0 Tohoku-oki earthquake, and observation of the huge slip of the Tohoku-oki earthquake near the trench using GPS-acoustic methods has considerably advanced our knowledge of stress release and accumulation in this subduction zone. [ABSTRACT FROM AUTHOR]

The method was numerically tested for two large underthrust fault models, a giant earthquake ( I M i SB w sb 8.8) and the Nemuro-oki earthquake ( I M i SB w sb 8.0) models along the Kurile arc subduction zone. Katsumata and Nakatani ([4]) tested the seismic quiescence hypothesis through retrospective trials of alarm-based earthquake prediction in the Kurile-Japan subduction zone. 10.1186/s40623-020-01293-0 4 Katsumata K, Nakatani M. Testing the seismic quiescence hypothesis through retrospective trials of alarm-based earthquake prediction in the Kurile-Japan subduction zone. [Extracted from the article]

Abstract: We examined GPS data in the northwestern Pacific region, which includes the Izu–Ogasawara (Bonin)–Mariana (IBM) arc and the Japan arc. GPS velocity vectors on the Izu Islands, including Hachijo-jima and Aoga-shima, show systematic eastward movement deviating from that predicted by the rigid rotation of the Philippine Sea plate; this deviation supports the active back-arc spreading model suggested by previous geological studies. The results of a statistical F-test analysis with 99% confidence level showed that the forearc of the Izu Islands arc has an independent motion with respect to the rigid part of the Philippine Sea plate. We developed a kinematic block–fault model to estimate both rigid rotations of crustal blocks and elastic deformation due to locked faults on the block boundaries. The model suggests that the back-arc opening rate along the Izu back-arc rift zone ranges from 2mm/yr at its southern end to 9mm/yr near Miyake-jima, its northern end. It also predicts 23–28mm/yr of relative motion along the Sagami Trough in the direction of ~N25°W, where the Izu forearc subducts beneath central Japan. The orientation of this motion is supported by slip vectors of recent medium-size earthquakes, repeated slow-slip events, and the 1923 M=7.9 Kanto earthquake. [Copyright &y& Elsevier]

Most large earthquakes occur along an oceanic trench, where an oceanic plate subducts beneath a continental plate. Massive earthquakes with a moment magnitude, Mw, of nine have been known to occur in only a few areas, including Chile, Alaska, Kamchatka and Sumatra. No historical records exist of a Mw = 9 earthquake along the Japan trench, where the Pacific plate subducts beneath the Okhotsk plate, with the possible exception of the ad 869 Jogan earthquake, the magnitude of which has not been well constrained. However, the strain accumulation rate estimated there from recent geodetic observations is much higher than the average strain rate released in previous interplate earthquakes. This finding raises the question of how such areas release the accumulated strain. A megathrust earthquake with Mw = 9.0 (hereafter referred to as the Tohoku-Oki earthquake) occurred on 11 March 2011, rupturing the plate boundary off the Pacific coast of northeastern Japan. Here we report the distributions of the coseismic slip and postseismic slip as determined from ground displacement detected using a network based on the Global Positioning System. The coseismic slip area extends approximately 400?km along the Japan trench, matching the area of the pre-seismic locked zone. The afterslip has begun to overlap the coseismic slip area and extends into the surrounding region. In particular, the afterslip area reached a depth of approximately 100?km, with Mw = 8.3, on 25 March 2011. Because the Tohoku-Oki earthquake released the strain accumulated for several hundred years, the paradox of the strain budget imbalance may be partly resolved. This earthquake reminds us of the potential for Mw???9 earthquakes to occur along other trench systems, even if no past evidence of such events exists. Therefore, it is imperative that strain accumulation be monitored using a space geodetic technique to assess earthquake potential. [ABSTRACT FROM AUTHOR]

Abstract: We present a map of the coseismic displacement field and slip distributions resulting from the Yushu earthquake on 14 April 2010 in Qinghai, China. The wide coverage of ScanSAR data helps in increasing the opportunity of interferometric synthetic aperture radar (InSAR) observations of a specific location on Earth, estimating surface slip, and constraining slip distribution on the fault plane. We increased InSAR sensitivity to the horizontal and vertical surface displacements by combining ascending and descending interferograms. We find that the maximum left-lateral surface slip is 166cm at ~9.7km WNW of Yushu. The end-to-end length of surface and subsurface faults is about 73km, and the estimated lengths of the two surface fault lines are 30km and ~9km. Slip distribution on a fault plane inverted from InSAR data shows an almost pure left-lateral strike-slip, with two slip peaks near the epicentres and Yushu and a maximum slip of ~2.6m. No postseismic deformation is observed southeast of the source region; however, we detected a significant postseismic displacement northwest of the source region. The deformation area is located a few kilometres northwest of the coseismic displacement area observed around Longbao Lake, suggesting that the coseismic slip and the postseismic slips are spatially isolated. [Copyright &y& Elsevier]

Temporal change of deformation in northeastern Japan is clarified by continuous Global Positioning System (GPS) observations from 1995 April to 2002 March. The observed GPS velocity is approximately parallel to the direction of plate convergence on east and west plate boundaries of northeastern Japan and shows post-seismic transient deformation around source regions of the Hokkaido-Nansei-Oki and the Sanriku-Haruka-Oki earthquakes. We interpret the source of the observed deformation as contemporary interplate coupling on the east subducting boundary to the Pacific Plate and the west collision boundary to the Amurian Plate. Using elastic dislocation theory, we inverted horizontal and vertical velocities of 212 GPS stations to estimate interplate coupling on both boundaries. The estimated coupling during 1995–2002 is spatially heterogeneous, however, it is temporally almost constant except for the region around the 1993 and 1994 earthquakes. After-slip of the 1994 earthquake occurred over the coseismic rupture area and its downdip extension on the plate boundary for 0.3–1.3 yr after the earthquake. After-slip continued only in the downdip extension for later periods and decayed with time. Weak coupling was recovered in the eastern part of the coseismic rupture area 3.3 yr after the earthquake. Interplate coupling on the Pacific Plate was strong in two regions, Miyagi-Oki and Tokachi-Oki. The west plate boundary is tightly coupled except for the source areas of three large earthquakes that occurred in 1964, 1983 and 1993. The apparent decoupling of the source areas of these earthquakes implies long-term post-seismic deformation as a result of viscoelastic relaxation in the subseismogenic lithosphere. [ABSTRACT FROM AUTHOR]

Correction to: Earth Planets Space (2021) 73:122 https://doi.org/10.1186/s40623-021-01439-8 Following publication of the original article (Tanioka et al. [1]), the authors reported an error in the third reference. References 1 Tanioka Y, Uchida N, Gusman AR, Shishikura M, Nishimura T. Special issue, "Kurile arc subduction zone: View of great earthquake generation and disaster mitigation of related phenomena". [Extracted from the article]

A moment magnitude Mw9.0 earthquake hit northeastern Japan at 14:46:18 (Japan Standard Time), March 11, 2011. We have obtained 1 s precise point positioning solutions for 1198 GEONET stations. Although GPS position time series have been routinely investigated and used as waveforms for dynamic inversion of earthquakes, we focus on exploring the spatial displacement features of GEONET stations for this earthquake. A movie inspection of high-rate GPS waveforms leads us to find that 76.21% of the GEONET stations in the Japanese islands subsided suddenly within 1 s between 14:59:45 and 14:59:46, Japan local time, with an average displacement of - 2.43 , 2.83 and - 4.75 mm in the east, north and vertical components, respectively, about 15 min after the 2011 Tohoku earthquake. We have performed different types of independent tests, namely measurement error analysis, processing the GEONET data with a different software system, a statistical hypothesis testing under a simple assumption of sign distributions, the test computation of the displacement field outside of the Japanese islands and an independent test with the Japanese strong motion borehole network KiK-net, to see whether these sudden movements actually occurred. The first four independent tests are passed almost without any doubt, and the direction of the average sudden displacements is roughly consistent tectonically with the direction of subduction of the Pacific plate. Because there are only 78 KiK-net borehole stations available for an independent seismic test, the KiK-net results are marginally consistent with those of GEONET. In the daily seismological and geophysical practice, one may then conclude that the sudden movement within the second is real after passing these five independent tests. However, a further epoch-by-epoch check pinpoints a few more seconds with even a higher probability of sudden displacement from the 20-min three-component high-rate GPS waveforms after the main shock, or more precisely, the seconds between 14:59:04 and 14:59:05, 15:01:04 and 15:01:05, and 15:03:39 and 15:03:40 with 80.80, 84.14 and 85.89% of the GEONET stations simultaneously moving upward, southward and westward, respectively. Although these probabilities are very high, it may hardly be imagined that a large scale of sudden movements could occur repeatedly between 14:59:04 and 15:03:40. The high-rate GPS results imply that some detected sudden movements after the earthquake could be unidentified artifacts of GPS data processing, though we cannot rule out the possibility that the detected sudden movements in Japan after the 2011 Tohoku Mw9.0 earthquake are real physical signals. [ABSTRACT FROM AUTHOR]

Ultrabroadband seismograms recorded by one-second-sampling global navigation satellite system (GNSS) and a stress meter provided the first opportunity for us to track unique and rare phases in wave propagation phenomena associated with the 2011 Mw9.1 Tohoku earthquake. We compare sea-level records along the opposite coast to the earthquake source area with the GNSS displacement seismograms at nearby stations. These provide new evidence that the short-period tsunami forerunner with periods of 70 to 100 s was probably initiated by the huge horizontal seismic motion on the dipped seafloor. In the southernmost part of the Boso and the Miura peninsulas outside of the Kanto Basin, distinctive oscillations with periods of 15 to 20 s and peak-to-peak amplitudes of up to 1 m followed the huge SH pulse of a width of 35 to 50 s on the GNSS displacement seismograms. This is believed to be a resonance of the 15 to 20 km-thick Neogene accretionary complex driven by the SH pulse. Analysis of continuous-stress seismograms at a borehole observation site of the Tono Research Institute of Earthquake Science ~ 600 km southwest of the epicenter shows the presence of two kinds of resonance. One is resonance of the island arc crust of Japan lasting for hours with dominant periods of 10 to 17 s. The other is whole-mantle resonance consisting of a succession of normal Rayleigh-wave dispersions circling the Earth lasting for more than 1 day with periods of 500 to 1000 s. [ABSTRACT FROM AUTHOR]