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A study of slow slip events is important in understanding the mechanism and friction properties of plate interfaces. We imaged the state of plate interface between the subducting Philippine Sea plate and overriding Amur plate beneath Shikoku Island, Japan, by applying a network inversion filter to the position time series of the Global Navigation Satellite System from January 2018 to April 2022. The results of network inversion filtering show 14 short-term slow slip events associated with low-frequency earthquakes along with long-term slow slip events in the Bungo Channel, central Shikoku, and Kii-channel Japan. The long-term slow slip events in the Bungo, central Shikoku, and Kii-channels are spatially separated from each other, suggesting independent events. The recurrence interval of the central Shikoku slow slip event remains unclear. A Kii-channel slow-slip event occurs with an irregular recurrence interval. The estimated moments of the Bungo, central Shikoku, and Kii-channel slow slip events were Mw7.0, Mw6.5, and Mw6.3, respectively, with a rigidity of 30 GPa. The estimated moment magnitude of the short-term slow slip events ranges from Mw5.4 to Mw6.2. The major detected short-term slow slip events are consistent with the detected events from tilt meter analysis by the National Institute of Earth Science and Disaster Resilience of Japan. Most of the detected slow slip events are associated with low-frequency earthquakes, and some exhibited spatial propagation. Spatio-temporal relationship between low-frequency earthquakes and aseismic slip may provide us with the insight into the physical processes between them.

Reservoirs accumulate and evolve magma during decades to centuries under Canary Islands volcanoes. Finally, magma migrates towards the surface before eruptions. However, little is known about the pathways and mechanisms controlling this migration. Past low eruption recurrence rate and the fact that the most recent 2011-2012 El Hierro eruption was off-shore hampered us to fully understand the magma(s) migration process. During the 2021 Cumbre Vieja eruption eruptible magmas showed remarkable mobility during the preceding 8 days before the eruption on the 13th of September 2021. This magma migration was reflected as surface ground deformation and seismicity. We used satellite radar interferometry to track 1) the geometry of the active magmatic reservoirs, and 2) the dynamics of magma emplacement and migration. To further, speculate about the reasons for that geometry and dynamics. Hence, the 2021 Cumbre Vieja eruption represents a unique opportunity to learn more about the mechanisms that facilitate magma migration beneath these volcanoes, and compare it with similar basaltic volcanoes. Our work aims to contribute knowledge that will help hazard assessment and volcanic risk reduction.

Long-term deformations of the Kusatsu-Shirane and Asama volcanoes in central Japan were investigated using Global Navigation Satellite System (GNSS) measurements. Large postseismic deformations caused by the 2011 Tohoku earthquake — which obscure the long-term volcanic deformations — were effectively removed by approximating the postseismic and other recent tectonic deformations in terms of quadrature of the geographical eastings/northings. Subsequently, deformation source parameters were estimated by the Markov Chain Monte-Carlo (MCMC) method and linear inversion. The deformation source of the Kusatsu-Shirane volcano was found to be a sill-like oblate spheroid located a few kilometers northwest of the Yugama crater at a depth of approximately five km, while that of Asama was also estimated to be a sill-like oblate spheroid located at the western flank of the edifice at a depth of approximately 13 km, along with the previously reported shallow east-west striking dike at a depth of approximately 1 km. It was revealed that 1) volume changes of the Kusatsu-Shirane deformation source and the shallow deformation source of Asama were correlated with the volcanic activities of the corresponding volcanoes, and 2) the Asama deep source has been steadily losing volume, which may indicate that the volcano will experience less eruptions in the near future.

Since the establishment in 2013, GGOS Japan, formerly known as GGOS Working Group of Japan, has actively contributed to domestic and international space-geodetic activities. Until it was established, six Japanese agencies with their own backgrounds and missions had individually conducted geodetic observations of GNSS, VLBI, SLR, DORIS and gravimetry in Japan and Antarctica. GGOS Japan was established to strengthen the collaboration between the agencies and to get connected to international organizations such as IAG and GGOS.Its core members consist of a chair, a secretary, a lead of the outreach working group, a lead of the DOI working group and representatives of five core techniques. It is supported by tens of people in Japan and also by its parent entity, IAG subcommittee in Japan.This presentation will cover our achievement such as assembling our site list, hosting various domestic/international meetings, planning a special issue in a domestic journal, producing its leaflet and website and so on. Since 2017 it has been approved as an GGOS Affiliate and it is remarkable that Basara Miyahara was elected as GGOS President in 2019.

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.

Currently, the Geospatial Information Authority of Japan routinely operates the GNSS analysis system to produce coordinate solutions using a GNSS station network called GEONET. The sampling rate of these coordinate solutions is 1 day, or 3 hours at the highest. To augment the system to produce coordinate solutions with higher temporal resolution, a GNSS analysis system to produce kinematic coordinate solutions using the GEONET stations has been developed. This analysis system adopts the precise point positioning strategy to make the system robust and lightweight. In fact, the system is so lightweight that it can be operated with two personal computers. The system produces three types of coordinate solutions with intervals of 30 s, depending on their latency. Each coordinate solution has a quality represented by a typical coordinate repeatability of 1 cm in horizontal components. The system has been successfully utilized in constructing a fault model of the 2016 Central Tottori Earthquake. In the future, the system will be updated to host capacities for 1) producing post-processing 1 s coordinate solutions and 2) producing real-time 1 s coordinate solutions.

Phreatic eruptions are caused by pressurization of geothermal fluid sources at shallow levels. They are relatively small compared to typical magmatic eruptions, but can be very hazardous. However, owing to their small magnitudes, their occurrences are difficult to predict. Here we show the detection of locally distributed ground inflation preceding a small phreatic eruption at the Hakone volcano, Japan, through the application of interferometric synthetic aperture radar analysis. The ground inflation proceeded the eruption at slow speed of ∼5 mm/month with a spatial size of ∼200 m in the early stage, and then it accelerated 2 months before the eruption that occurred for the first time in 800–900 yrs. The ground uplift reached ∼30 cm, and the eruption occurred nearby the most deformed part. The deformation speed correlated well with inflation of spherical source located at 4.8 km below sea level, thus suggesting that heat and/or volcanic fluid supply from the spherical source, maybe magma reservoir, directly drove the subsurface hydrothermal activity. Our results demonstrate that high-spatial-resolution deformation data can be a good indicator of subsurface pressure conditions with pinpoint spatial accuracy during the preparatory process of phreatic eruptions.

Our 3-D electrical resistivity model clearly detects particular subsurface features for magmatism associated with subduction of the Philippine Sea Plate (PSP) in three regions: a southern and a northern volcanic region, and a non-volcanic region on the island of Kyushu. We apply 3-D inversion analyses for geomagnetic transfer function data of a short-period band, in combination with results of a previous 3-D model that was determined using Network-Magnetotelluric response function data of a longer-period band as an initial model in the present inversion to improve resolution at shallow depths; specifically, a two-stage inversion is used instead of a joint inversion. In contrast to the previous model, the presented model clearly reveals a conductive block on the back-arc side of Kirishima volcano at shallow depths of ~50 km; the block is associated with hydrothermal fluids and hydrothermal alteration zones related to the formation of epithermal gold deposits. A second feature revealed by the model is another conductive block regarded as upwelling fluids, extending from the upper surface of the PSP in the mantle under Kirishima volcano in the southern volcanic region. Third, a resistive crustal layer, which confines the conductive block in the mantle, is distributed beneath the non-volcanic region. Fourth, our model reveals a significant resistive block, which extends below the continental Moho at the fore-arc side of the volcanic front and extends into the non-volcanic region in central Kyushu.

Real-time geopotential measurements with two synchronously linked optical lattice clocks are demonstrated. A height difference between the two clocks separated by 15 km is determined, with an uncertainty of 5 cm, by means of a gravitational redshift. According to Einstein's theory of relativity, the passage of time changes in a gravitational field1,2. On Earth, raising a clock by 1 cm increases its apparent tick rate by 1.1 parts in 1018, allowing chronometric levelling3 through comparison of optical clocks1,4,5. Here, we demonstrate such geopotential measurements by determining the height difference of master and slave clocks separated by 15 km with an uncertainty of 5 cm. A subharmonic of the master clock laser is delivered through a telecom fibre6 to synchronously operate7 the distant clocks. Clocks operated under such phase coherence reject clock laser noise and facilitate proposals for linking clocks8,9 and interferometers10. Taken over half a year, 11 measurements determine the fractional frequency difference between the two clocks to be 1,652.9(5.9) × 10−18, consistent with an independent measurement by levelling and gravimetry11. Our system demonstrates a building block for an internet of clocks, which may constitute ‘quantum benchmarks’, serving as height references with dynamic responses.

During the 2000 eruption of the Miyakejima volcano in Japan, step-like tilt changes (TC) generally accompanied by very long period (VLP) seismic signals with a pulse-like shape and widths of ∼50 s were repeatedly observed (TC/VLP events). Kinematic GPS time series for Miyakejima were investigated in order to detect displacements associated with these events. We found that the kinematic GPS time series could be interpreted as the superposition of the following features: (1) displacement associated with the TC/VLP events, the source of which possibly corresponded to a shallow magma chamber represented by an almost vertical ellipsoidal cavity elongated NE–SW at a depth of 2–3 km; (2) displacement following TC/VLP events that may have been caused by exponential-type volume decreases of the same magma chamber with a decay constant of approximately half a day; and (3) displacements that may be caused by continuous volume decreases of the same magma chamber. These features broadly support the piston model of VLP seismic signals, in which a vertical piston of solid conduit material intermittently sinks into a magma chamber located a few kilometer beneath the edifice following deflation caused by continuous outflux of magma. The volume increase of the magma chamber associated with the TC/VLP events was found to be much smaller than that of the collapsed caldera, suggesting that most of the mass in the conduit sank into the magma chamber without generating VLP seismic waves or step-like TC.

The sub-daily noise in horizontal global positioning system (GPS) kinematic time series arising from monument tilts is quantitatively evaluated using tiltmeter data at GPS stations from the Japanese nationwide global navigation satellite system network. The estimated tilt-induced monument displacements show characteristics that are typical of those caused by thermal tilts of the monuments. The root mean square of the displacements is typically a few millimetres, with notable inter-seasonal variations. The stacked amplitude spectra of the monument displacements have peaks at the tidal bands S1 and S2, and their higher tones. The peaks at the S1 and S2 bands in the amplitude spectra are reduced by 41 and 43 % for the north–south component and 36 and 53 % for the east–west component, respectively, after correcting for the monument displacements. The monument displacements due to the thermal tilts of the monuments may also be a favourable candidate for sub-daily noise at the S1 and S2 bands found in other GPS networks.

A new continuous GPS station, 06S061, was installed in Tsukuba, Japan, which is directly anchored to the soil at a depth of 190 m, so that it is less affected by seasonal poroelastic deformations of aquifers induced by groundwater extraction for irrigation. A comparison of GPS-derived vertical movements of surrounding GPS stations relative to 06S061 with the independent observations revealed that 06S061 has an observation quality comparable to a standard GPS station in terms of coordinate repeatability. The poroelastic deformations of aquifers below 190 m recorded at 06S061 were estimated to have peak-to-peak values of about 1 cm, which is half of the total poroelastic deformations of aquifers observed at surrounding GPS stations.

The Global Navigation Satellite System (GNSS) has been utilized in a variety of research fields within the geosciences. This research has been further developed for application to hazard monitoring and natural disaster mitigation. Some developments have even been implemented in society in countermeasures against natural disasters. The Geospatial Information Authority of Japan (GSI), for example, has established a nationwide GNSS network called GEONET. The data from GEONET are used extensively among researchers and practitioners, not only for basic research but also for the development of methods and systems that can mitigate disasters. This special volume is a collection of articles that discuss how such methods and systems are now being developed and/or planned to both clarify the mechanisms behind natural hazards and mitigate the damage they may cause. The volume consists of 13 papers covering a wide range of natural phenomena, such as earthquakes, crustal movements, tsunamis, ionospheric disturbances, and volcanic eruptions. Some papers help us to understand how natural hazards behave, which should be the first step toward disaster mitigation. On the other hand, other articles report direct efforts made toward providing early warnings of impending disasters. Disaster mitigation systems may require real-time (and even kinematic with high-rate data sampling) processing and dissemination of data. Moreover, some applications involve data collection from coastal waters and the open sea. Now that the density of GNSS stations has approached saturation on land, the scarcity of data collected offshore will have to be rectified through the development of GNSS systems in the ocean. We do hope that this volume will be a step in the further progress of utilizing GNSS for disaster monitoring and mitigation in the future to make society safer and more secure.

Troposphere-induced errors in GPS-derived geodetic time series, namely, height and zenith total delays (ZTDs), over Japan are quantitatively evaluated through the analyses of simulated GPS data using realistic cumulative tropospheric delays and observed GPS data. The numerical simulations show that the use of a priori zenith hydrostatic delays (ZHDs) derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather model data and gridded Vienna mapping function 1 (gridded VMF1) results in smaller spurious annual height errors and height repeatabilities (0.45 and 2.55 mm on average, respectively) as compared to those derived from the global pressure and temperature (GPT) model and global mapping function (GMF) (1.08 and 3.22 mm on average, respectively). On the other hand, the use of a priori ZHDs derived from the GPT and GMF would be sufficient for applications involving ZTDs, given the current discrepancies between GPS-derived ZTDs and those derived from numerical weather models. The numerical simulations reveal that the use of mapping functions constructed with fine-scale numerical weather models will potentially improve height repeatabilities as compared to the gridded VMF1 (2.09 mm against 2.55 mm on average). However, they do not presently outperform the gridded VMF1 with the observed GPS data (6.52 mm against 6.50 mm on average). Finally, the commonly observed colored components in GPS-derived height time series are not primarily the result of troposphere-induced errors, since they become white in numerical simulations with the proper choice of a priori ZHDs and mapping functions.

SUMMARY We quantitatively estimate the spurious annual vertical deformations due to the mismodelling of tropospheric delays over Japan, through a numerical simulation. For this purpose, we simulate the GPS data for present-day satellite distributions, using realistic cumulative tropospheric delays that are calculated using ray tracing and numerical weather models. To obtain the spurious deformations, the simulated GPS data are then analysed by using the same GPS processing software and the same analysis strategies as those used in the analysis of the observed GPS data. In the estimated spurious annual vertical deformations, it is found that the amplitudes of the deformations increase toward the north, reaching up to 3 mm at around 45 ◦ N, whereas the phase lags are uniform throughout Japan and vary by around 220 ◦ , indicating spurious subsidence in the middle of February. In the western part of Japan, the observed annual vertical deformations are less affected by spurious annual vertical deformations and more likely caused by the atmospheric and oceanic loading. In the northern part of Japan, we observe large (up to 8 mm) annual vertical deformations with phase lags corresponding to subsidence in winter; subsidence in winter is interpreted to be the effect of snow loading. However, some part of the observed subsidence is found to be spurious due to the mismodelling of the tropospheric delays. These spurious signals may be mitigated by using mapping functions that are constructed by using direct ray tracing and numerical weather models in the GPS analysis.

Time-domain electromagnetic (TDEM) surveys were carried out around Unzen Volcano, Shimabara Peninsula, South-west Japan in 2001 and 2002 in the eastern part of the peninsula. The surveys were a completion of the previously interpreted TDEM data collected from surveys in 1995 in the western part of the peninsula. Interpretation of the recorded transient magnetic fields resulted in a general feature of the resistivity structure which are composed of three main layers: a resistive surface layer, a conductive layer (below 10 Ωm) from about sea level to 2.5 km below the surface, and a third resistive layer. The conductive layer is considered to be a complex of water-saturated and altered layers which spreads widely beneath Shimabara Peninsula. The spatial conductance distribution shows a W–E trending pattern of high conductance from Tachibana Bay to the summit of Unzen (Fugen–Dake). This evidence indicates that volcanic gas was supplied to shallow layer in the western part of the peninsula, which is in accordance with the path of magma migration derived from seismic and deformation studies. Another high conductance zone was also found near Mayu–Yama in the eastern part of Shimabara Peninsula, indicating magma degassing process due to the possibility of the presence of a magma system beneath it.

SUMMARY We developed a semi-analytical method to evaluate the effect of the second-order ionospheric correction on GPS positioning. This method is based on the semi-analytical positioning error simulation method developed by Geiger and Santerre in which, assuming the continuous distribution of the satellites, a normal equation is formed to estimate the positioning error taking all the contributions of the ranging error by the visible satellites into account. Our method successfully reproduced the averaged time-series of three IGS sites which is comparable to the rigorous simulation. We then evaluated the effect of the ionospheric error on the determination of the reference frame. We evaluated the additional Helmert parameters that are required for the ionospheric effect. We found that the ionospheric effect can lead to annual scale changes of 0.1 ppb, with an offset of 1.8 mm and a semi-annual oscillation of 1 mm in the z-direction. However, these values are too small to explain the current deviations between the GPS-derived reference frame and the ITRF reference frame. Next, we estimated the apparent scale changes due to the ionospheric error in the GEONET coordinate time-series in Japan. We could qualitatively reproduce the observed semi-annual scale changes peaking at the equinoxes and having asymmetrical amplitudes between the vernal and autumnal equinoxes.

Summary In magnetotelluric (MT) studies, the observed response function (the MT impedance) usually suffers from galvanic distortions due to near-surface inhomogeneities. Removal of these effects is essential to obtain an accurate model of the subsurface electrical conductivity structure. Galvanic distortion is usually expressed by a simple real tensor multiplying the undistorted regional impedance. The problem still remains of how to solve the ensuing linear equations in order to determine the distortion tensor and then to obtain the undistorted impedance. The methods presented and widely applied in previous works assume two-dimensionality for the undistorted impedance. This paper proposes a method that employs a relationship between the spatial derivatives of the horizontal electric field and the vertical geomagnetic component, which can be directly derived from Faraday’s law. The identity derived from the relationship is written using the vertical magnetic transfer function, the impedance, and the spatial derivatives of the impedance and horizontal magnetic transfer functions. The present method determines the real distortion tensor so that the identity is satisfied. Therefore, the method has two major advantages: (1) galvanic distortion that is to be removed from the impedance tensor is clearly defined, and (2) the method is applicable even when the regional structure is 3-D.

[1] We estimated the spatial and temporal evolution of the preceding aseismic slip from January 2003 to January 2011, the coseismic slip of the Tohoku earthquake, and the postseismic slip after the earthquake based on global positioning system (GPS) data. Time-dependent analysis indicates aseismic slip offshore of Miyagi and Fukushima prefectures from 2004 associated with a series of subduction earthquakes that overlap the aseismic slip area. These preceding aseismic and coseismic slip areas are centered between the centers of the coseismic and afterslip areas of the Tohoku earthquake offshore of Miyagi prefecture, while they overlap the coseismic and afterslip areas of the Tohoku earthquake off Fukushima prefecture. The timing of moment magnitude nine (Mw9) -class earthquakes appears to be controlled by multiple preceding slip events, smaller earthquakes and their afterslip. The preceding aseismic and coseismic slip decreased the coupling rate off the Tohoku coast, suggesting the possibility that the preceding slip represented a precursive stage of the Tohoku earthquake. The afterslip of the Tohoku earthquake occurred in an area where the coseismic slip was not large, complementing the large coseismic slip zone. The afterslip along Iwate-Miyagi extends up to 80 km in depth and is currently the sole mechanism of strain release in this depth range. The source region of the anticipated Miyagi-Oki earthquake shows small postseismic slip after the Tohoku earthquake, reflecting the energy release at the time of the earthquake. Aftershock activity is roughly governed by an afterslip process.

[1] Global Positioning System (GPS) allows the detection of ionospheric disturbances associated with the vertical displacements of most of the major shallow seismic events. We describe a method to model the time and space distributions of Rayleigh wave induced total electron content (TEC) patterns detected by a dense GPS array. We highlight the conditions for which a part of the ionospheric pattern can be directly measured, at teleseismic distance and above the epicenter. In particular, a satellite elevation angle lower than 40° is a favorable condition to detect Rayleigh wave induced ionospheric waves. The coupling between the solid Earth and its atmosphere is modeled by computing the normal modes of the solid Earth–atmosphere system. We show the dependency of the coupling efficiency on various atmospheric conditions. By summation of the normal modes we model the atmospheric perturbation triggered by a given earthquake. This shows that a part of the observation is a Rayleigh-induced radiation pattern and therefore characteristic of the seismic rupture. Through atmosphere-ionosphere coupling, we model the ionospheric perturbation. After the description of the local geomagnetic field anisotropic effects, we show how the observation geometry is strongly affecting the radiation pattern. This study deals with the related data for two earthquakes with far-field and near-field observations using the Japanese GPS network GEONET: after the 12 May 2008 Wenchuan earthquake (China) and after the 25 September 2003 Tokachi-Oki earthquake (Japan), respectively. Waveforms and patterns are compared with the observed TEC perturbations, providing a new step toward the use of ionospheric data in seismological applications.

[1] We compared the mass variations from Gravity Recovery and Climate Experiment (GRACE) with those measured by bottom pressure recorders (BPRs) deployed as tsunami gauges. Prior to the comparison, we estimated the degree-1 Stokes coefficients by the degree-1 loading method using both the GPS and GRACE data. We successfully recovered the degree-1 Stokes coefficients that are consistent with those from the satellite laser ranging analysis and from the loading model. We found that the use of the GRACE data in the degree-1 loading method significantly mitigates the aliasing effect from the unmodeled higher-degree loading deformations. Then, we compared the mass variations from GRACE with those from the five BPRs that have been deployed as part of the Deep-ocean Assessment and Reporting of Tsunamis (DART) system. We observed a fairly good (over 0.4) correlation except for one station that is close to the U.S. mainland. However, we found that the GRACE-derived mass variations underestimate those from BPRs by nearly a factor of 2. Through numerical simulation, we found that the artificial leakage from the landmass is responsible for the low correlation observed at the station, and the spatial averaging in the GRACE processing may be responsible for the underestimation of the mass variations from BPRs by GRACE. These results illustrate the importance of performing a simulation for these effects with numerical models before comparing the GRACE-derived mass variations with those from pointwise measurements.

[1] The anomalous vertical movements observed in Tsukuba and their relevance to groundwater level changes are investigated. First, we investigated the vertical coordinate time series of an IGS station TSKB w.r.t. a nearby stable site and found that the time series has a strong correlation with the groundwater level changes of the deep wells. Next, we investigated those of the GPS antenna attached at the tip of the antenna of Tsukuba VLBI station w.r.t. TSKB. We found that the time series is decomposed into components that have 1) high correlation with the groundwater level changes of the shallow wells, and 2) high correlation with the air-temperature. Poroelastic movements of aquifers due to groundwater level changes and thermal expansion of the VLBI antenna are likely for the mechanisms of these high correlations.

[1] The effect of nontidal ocean mass loading is investigated as a possible cause for the seasonal variability observed in the vertical components of the GPS-derived site coordinates of tropical Pacific islands. The nontidal ocean mass origin sea level changes (MOSLCs) are estimated by subtracting the steric height changes observed at buoys from the net sea level changes measured by satellite altimetry. Assuming a linear relationship between the MOSLCs at the closest buoys and the GPS vertical movements, the coherences and the admittances are estimated. We found evidence that the vertical movements are caused by the loading effect at three out of four sites. The occasional deviations between the vertical movements and predicted loading deformations are presumably due to the invalidity of the assumption of a linear relationship between the MOSLCs and the loading deformation and/or of the mean temperature-salinity relationship used in estimating steric heights in the corresponding periods.

The large displacement induced by the 2011 M 9.0 off the Pacific coast of Tohoku Earthquake was observed by GPS stations of the permanent GPS Earth Observation Network system (GEONET) in northeastern Japan. The displacement was characterized by the eastward displacement and subsidence in the Pacific coastal area. The horizontal displacement exceeded 5.3 m, which is the largest ever detected by GEONET. The mainshock was followed by a sequence of aftershocks. We processed the GPS data through a kinematic positioning strategy to clarify the deformation, including the deformation caused by the mainshock, with high temporal resolutions. The offsets calculated from the kinematic coordinates separately depict the coseismic displacements of the mainshock, the largest aftershock, and the third largest. The fault model for these earthquakes suggests that the largest (M 7.7) and third largest (M 7.3) aftershocks ruptured the southern and northern extensions of the mainshock fault, respectively.