Geospatial Information Authority Of Japan Research Articles

Digital photogrammetry and GIS-based analysis of the bio-geomorphological evolution of Sakurajima Volcano, diachronic analysis from 1947 to 2006

The Sakurajima Volcano is one of the most active volcanoes in the world with regular activity dominated by vulcanian eruptions since 1955. Located in Kagoshima Prefecture – Kyushu Island, Japan – the Sakurajima Volcano is a stratovolcano with two main vents at the summit, the Kitadake and the Minamidake, and a third smaller central vent, the Nakadake. The two firsts peak at 1117 and 1060m dominate the slopes mainly composed of lava-flow deposits, secondary volcaniclastic material and recent ejectas from the Vulcanian eruptions. Although the volcano has been very closely monitored by Japanese Universities (mostly Kyoto University and Kagoshima University) and governmental agencies, there has been very little geomorphological investigation of the structure of the volcano. Using the digital photogammetric method SfM–MVS (Structure from Motion and Multiple-view Stereophotogrammetry) applied to historical aerial photographs, the present contribution aims to provide an analysis of the volcanic structure and the recent bio-geomorphological evolution for the period 1947–2006. First, the results have proved that SfM–MVS is a method that can be successfully applied to aerial photographs for diachronic reconstruction of geomorphological landscape evolution. This method is especially important in active volcanic areas, as the geomorphology can change very rapidly within the historical period. Secondly, the results have shown that during the last ~60years, the summit area of the Sakurajima has greatly evolved: the morpholology of the Minamidake crater has changed due to its regular explosive activity; the upper slopes have been covered in ejecta, modifying their elevation and their smoothness. The lower slopes have seen the apparition of lahar deposition areas, while valleys, upslope, have widened due to the lahar activity and the upward progression of the deposits. The 3D derived from SfM–MVS has also shown how the lahar deposits are using the topographic low, created on top of the lava deposits and in between lava deposit to accumulate mid-slopes, rather than accumulating on the lower volcanic apron. This is accentuated by the construction of SABO dams that keep a large amount of the material on the slopes. Finally, as this publication has been carried out using the freely available imagery from the GSI (Geospatial Information Authority of Japan) at 200dpi, higher resolution imagery can even open further possibilities for the monitoring of volcano evolution in Japan and in countries providing long series of historical imagery.

Three‐dimensional GPS ionospheric tomography over Japan using constrained least squares

AbstractA new three‐dimensional GPS ionospheric tomography technique is developed that uses total electron content (TEC) data from the dense Global Position System (GPS) receiver network, GPS Earth Observation Network (GEONET) in Japan, and it will not require an ionospheric model as the initial guess that will bias the reconstruction of electron density. The GEONET is operated by Geospatial Information Authority of Japan and consists of more than 1200 receivers; this high density and wide coverage helps to reconstruct the electron density distribution in the ionosphere with high spatial resolution. This tomography technique uses a constrained least squares fit to reconstruct the three‐dimensional electron density distributions. This method is different to most other techniques as they require a background ionospheric model as an initial guess that could bias the reconstructed electron density. It rather uses a prior condition that the electron density should not exceed a certain value that is determined by the restrain parameter, which is derived from the NeQuick model. Its independency of the initial guess from a model will make it useful even in disturbed conditions. This paper presents results that are obtained by using this new tomographic technique. The reconstruction of three‐dimensional ionospheric tomograms is demonstrated using the GPS data, and the reliability and robustness are checked with simulated tomograms obtained using the synthetic GPS‐TEC data produced using NeQuick model.

The signature of the 2011 Tohoku mega earthquake on the geomagnetic field measurements in Japan

On 11 March 2011 at 05:46:23 UTC, a mega earthquake (EQ) with magnitude (Mw) 9.0 [The 2011 Tohoku Earthquake] occurred at a depth of about 24km near the East coast of Honshu Island, Japan as a result of a thrust faulting on or near the subduction plate boundary between the Pacific and North American plates. Geomagnetic data from MAGDAS and Geospatial Information Authority of Japan (GSI) networks have been analyzed to examine the signature of the 2011 Tohoku earthquake on the geomagnetic field measurements in Japan. Results of data analysis indicate about 5nT increase in the total geomagnetic field intensity in the vicinity of the epicenter of 2011Tohoku EQ compared with other reference stations. Moreover, the annual range of the Z-component daily variations tends to decrease near the epicenter before the occurrence of the Tohoku EQ. Concerning the ULF emissions; the Pc 3 amplitude ratio (ZPc3/HPc3) near the epicenter at the Onagawa [ONW] station showed a good correlation with other remote reference stations before the Tohoku EQ but it started to decrease with no correlation to other stations a few weeks before the 2011 Tohoku EQ. On the other hand, the Pc 3 amplitude ratio at ONW station showed a clear anti-correlation compared with reference stations after the 2011 Tohoku EQ.

Geomagnetic Surveys by the Geospatial Information Authority of Japan and the Contribution of the Kakioka Magnetic Observatory

The Geospatial Information Authority of Japan (GSI) has been conducting geomagnetic surveys in Japan since 1949 to clarify the geographical distribution of direction, intensity of the geomagnetic field, and their secular variations. Recently, we have carried out continuous observations at geodetic observatories and continuous geomagnetic stations and repetitive observations at several first-order geomagnetic stations. The results of the surveys, “geomagnetic charts”, have been published every 10 years. In 2011, GSI released the newest geomagnetic charts for the epoch 2010.0 created by adopting a new spatial-temporal model. This model needs continuous data of good quality. In addition to the GSI geodetic observatories, the Kakioka Magnetic Observatory, which has been conducting high-quality and stable observations for 100 years, makes a large contribution.

６. 地上型レーザー計測のマニュアル案について

3D cloud point data using Terrestrial Laser Scanner has been spreading to survey for a decade. The Geospatial Information Authority of Japan (GSI), however, does not establish yet the official specifications in the Operation Specifications for Public Surveys. The object of the manual working group of K.I.T. Geospatial Information Project is to make specifications for Terrestrial Laser Scanner. This paper introduces the activity to make manual of Terrestrial Laser Scanner for public survey by KIT manual working group.

Dedicated to the Launch of the New 1/25,000 Topographic Map by the Geospatial Information Authority of Japan

Dedicated to the Launch of the New 1/25,000 Topographic Map by the Geospatial Information Authority of Japan

Wide-area land subsidence caused by “the 2011 Off the Pacific Coast of Tohoku Earthquake”

This paper gives an overview of the crustal deformation caused by “the 2011 off the Pacific Coast of Tohoku Earthquake” (hereinafter: “the Tohoku Earthquake”) as detected by the GPS Earth Observation Network (GEONET), a GPS continuous observation system operated by the Geospatial Information Authority of Japan (GSI), and of ground deformation resulting from liquefaction triggered by the earthquake motion as determined by a leveling survey. A very large part of the Japanese archipelago was affected by the crustal deformation caused by the mainshock. The subsidence in the Pacific coastal area of the Tohoku region is especially remarkable. Based on a resurvey after the earthquake, the GSI revised the coordinates and heights of survey marks, including the Origin of the Japanese Horizontal Control Network and the Origin of the Japanese Vertical Control Network. We estimated the geometry of the seismogenic fault of the Tohoku Earthquake, as well as a slip model for the boundary between the Pacific Plate and the North American Plate, based on crustal deformation data. Postseismic crustal deformation was also observed by GEONET. Even though the area that coseismicaly subsided is undergoing partial uplift from postseismic deformation, such uplift is not rapid enough to make up for the coseismic subsidence within the next several years.The earthquake caused liquefaction in large parts of the Kanto Region, especially on the Tokyo Bay side and at the lower reaches of the Tone River. Liquefaction was concentrated in areas of land reclamation and former river channels, where it is easy to recognize using time-series geospatial information such as olden topographic maps and olden aerial photographs. To determine the amount of land subsidence (cm) due to liquefaction in Urayasu City, the GSI carried out a leveling survey and compared the differences between pre- and post-earthquake LIDAR survey data with the relative subsidence obtained by leveling.

GEOGRAPHICAL INFORMATION ANALYSIS OF TSUNAMI FLOODED AREA BY THE GREAT EAST JAPAN EARTHQUAKE USING MOBILE MAPPING SYSTEM

Abstract. The great earthquake occurred in Tohoku District, Japan on 11th March, 2011. This earthquake is named "the 2011 off the Pacific coast of Tohoku Earthquake", and the damage by this earthquake is named "the Great East Japan Earthquake". About twenty thousand people were killed or lost by the tsunami of this earthquake, and large area was flooded and a large number of buildings were destroyed by the tsunami. The Geospatial Information Authority of Japan (GSI) has provided the data of tsunami flooded area interpreted from aerial photos taken just after the great earthquake. This is fundamental data of tsunami damage and very useful for consideration of reconstruction planning of tsunami damaged area. The authors analyzed the relationship among land use, landform classification, DEMs data flooded depth of the tsunami flooded area by the Great East Japan Earthquake in the Sendai Plain using GIS. Land use data is 100 meter grid data of National Land Information Data by the Ministry of Land, Infrastructure, Transportation and Tourism (MLIT). Landform classification data is vector data of Land Condition Map produced by GSI. DEMs data are 5 meters grid data measured with LiDAR by GSI after earthquake. Especially, the authors noticed the relationship between tsunami hazard damage and flooded depth. The authors divided tsunami damage into three categories by interpreting aerial photos; first is the completely destroyed area where almost wooden buildings were lost, second is the heavily damaged area where a large number of houses were destroyed by the tsunami, and third is the flooded only area where houses were less destroyed. The flooded depth was measured by photogrammetric method using digital image taken by Mobile Mapping System (MMS). The result of these geographic analyses show the distribution of tsunami damage level is as follows: 1) The completely destroyed area was located within 1km area from the coastline, flooded depth of this area is over 4m, and no relationship between damaged area and landform classification. 2) The heavily damaged area was observed up to 3 or 4km from the coastline. Flooded depth of this area is over 1.5m, and there is a good relationship between damaged area and height of DEMs. 3) The flood only area was observed up to 4 or 5km from the coastline. Flooded depth of this area was less than 1.5m, and there is a good relationship between damaged area and landform. For instance, a certain area in valley plain or flooded plain was not affected by the tsunami, even though an area with almost the same height in coastal plain or delta was flooded. These results mean that it is important for tsunami disaster management to consider not only DEMs but also landform classification.

Multi-Layer Ionospheric VTEC Estimation for GNSS Positioning

In this paper, the multi-layer ionospheric model based regional VTEC (Vartical Total Electron Content) estimation methods applied by GNSS (Global Navigation Satellite System) Regressive models (abbreviated as GR models) are presented. In the methods, the SCHA (Spherical Cap Harmonic Analysis) as well as the SHF (spherical harmonic functions) are also applied to model the regional VTEC distributions. The ionospheric delays (or advances) over Japan are estimated by using GEONET (Gps Earth Observation NETwork) data provided from the GSI (Geospatial Information Authority of Japan). By applying the ionospheric correction based on the multi-layer model, the positioning accuracy can be improved, and consequently the regional ionosphere can be modeled more accurately by the multi-layer model.

Mapping of Building Damage of the 2011 Tohoku Earthquake Tsunami in Miyagi Prefecture

The authors visually inspected the building damage caused by the 2011 Tohoku earthquake tsunami, using the pre and post-event aerial photos. First, we prepared the mosaic of post-tsunami aerial photos acquired by Geospatial Information Authority of Japan (GSI), and conducted the visual inspection of buildings damage to classify the damage. The damage classification results are compiled with building shape files on GIS for mapping the structural vulnerability in the tsunami inundation zone. Finally, we discussed the structural vulnerability in the tsunami affected area based on mapping results of building damage.

強震記録に基づく東北地方太平洋沖地震による地殻変動分布の算定

The 2011 off the Pacific coast of Tohoku Earthquake (M 9.0) is the greatest earthquake in Japan. Analysis of GPS network, such as GEONET by Geospatial Information Authority of Japan, has revealed the crustal deformation distribution due to the earthquake. On the other hand, the crustal deformation distribution can be estimated from the displacement waveform calculated by integrating the accelogram observed by strong motion seismometer. This method would be used complementary with GPS analysis. In this study, we calculated the crustal deformation distribution due to the 2011 off the Pacific coast of Tohoku Earthquake from the accelograms recorded on strong motion observation network K-NET and KiK-net by National Research Institute for Earth Science and Disaster Prevention. The crustal deformation distribution calculated from strong motion records is consistent with that by GPS observation. In addition, the displacement waveforms estimated from strong motion records are in good agreement with that from 1 Hz GPS analysis.

Numerical study of the effects of tsunamis using a finite element method

Effects of tsunamis generated in water areas surrounding Japan are studied numerically. Partial differential equations consisting of momentum equations and a continuity equation are reduced to a system of ordinary differential equations with discretisation based on a finite element mesh. An ordinary differential equation solver is applied to the resultant system to generate numerical solutions. Depth data formulated in terms of longitude and latitude in the horizontal direction are transformed to generate input data in terms of projected coordinates by the Gauss--Kruger projection. Numerical results are visualised, and effects of tsunamis such as wave heights and propagation speeds are illustrated. Numerical techniques to simulate tsunamis are described, and numerical results are introduced. References I. Aida. Numerical experiments for the tsunamis generated off the coast of the Nankaido district. Bull. Earthquake Research Institute , 56:713--730, 1981. J. D. Lambert. Computational Methods in Ordinary Differential Equations . John Wiley and Sons, Chichester, 1973. L. Mansinha and D. E. Smylie. The displacement fields of inclined faults. Bulletin of the Seismological Society of America , 61(5):1433--1440, October 1971. A. R. Mitchell and R. Wait. The Finite Element Method in Partial Differential Equations . John Wiley and Sons, Chichester, 1977. Geospatial Information Authority of JAPAN. The Niigata--Kobe tectonic zone. http://cais.gsi.go.jp/Virtual_GSI/Tectonics/Niigata_Kobe/niigata_kobe.html , January 14, 2011. T. Okamoto, M. Kawahara, N. Ioki, and H. Nagaoka. Two-dimensional wave run-up analysis by selective lumping finite element method. International Journal for Numerical Methods in Fluids , 14(1992):1219--1243, 1992. N. Shuto, F. Imamura, S. Koshimura, K. Satake, and H. Matsutomi. Encyclopedia of Tsunami . Asakura Shoten, 2007 (in Japanese).

Seismic and geodetic evidence for the existence of hot materials beneath the Wakayama swarm activity, southwestern Japan

A remarkable seismic swarm area exists amid the Wakayama Plain on the western coast of the Kii Peninsula, in southwestern Japan, close to the Median Tectonic Line (MTL). The hypocenters of these swarm earthquakes are very shallow with a median of 6 km. This is exceptionally shallow for seismic activity in plain areas where the seismogenic layer is usually deep compared to that in mountainous regions ( Takayama et al., 2006). Also, the b-value below 8 km in the eastern part of this swarm region is anomalously high. In addition to these seismic features, GEONET data and leveling survey data obtained by the Geospatial Information Authority of Japan indicate that land around the swarm region are expanded and upheaved. Areas of the dilatation and upheaval almost overlap and their centers correspond to the site where the high b-value anomaly is observed. These facts strongly suggest that there are hot materials beneath the source region. In the Kii Peninsula acid volcanic rocks outcrop widely, and the Wakayama swarm area is located on the southern side of the MTL in the metamorphic belt below which the relatively young hot Philippine Sea plate is subducting and dehydration from a surpentinized forearc mantle is expected to occur. Based on the seismic and geodetic observations and the tectonic background of the area in which the swarm region is situated, we propose a hypothesis that a diorite or a serpentine diapir with plentiful hot fluids might be intruding beneath the source area.

Countermeasures of the Geospatial Information Authority of Japan against the Great East Japan Earthquake

We report the countermeasure activities of the Geospatial Information Authority of Japan against the Great East Japan Earthquake in terms of monitoring of crustal deformation, grasping disasters by means of aerial photographs, photo interpretation, geographic analysis, providing related agencies with geospatial information, and others.

電子国土基本図（地図情報）の整備

Geospatial Information Authority of Japan (GSI) has started to maintain “Digital Japan Basic Map (Map Information),” and began broadcasting through the Internet since February 2011. Digital Japan Basic Map (Map Information) integrates information necessary for land management, such as topography and structure, into fundamental geospatial data such as roads and buildings for use as the nation's new basic land information, as a new fundamental map in digital age. This report shows some introduction to Digital Japan Basic Map (Map Information).

Data assimilation experiments of precipitable water vapour using the LETKF system: intense rainfall event over Japan 28 July 2008

We performed data assimilation experiments using data from an intense rainfall event in western Japan on 28 July 2008 with the Local Ensemble Transform Kalman Filter (LETKF) and analysed fields of the mesoscale four-dimensional variational assimilation (4DVAR) system of the Japan Meteorological Agency (JMA). We supplemented conventional observation data with precipitable water vapour (PWV) data derived from the Global Positioning System (GPS) Earth Observation Network of the Geospatial Information Authority of Japan. Because the LETKF system assimilates fewer data than the 4DVAR system, ensemble mean fields of the LETKF cycle experiment were replaced with analysed fields from the 4DVAR system each day at 12 UTC. PWV values were converted to relative humidity profiles for assimilation by the LETKF. The addition of PWV data tended to increase low-level water vapour and improve the precipitation forecast. We attempted to reproduce the intense rainfall band using downscale forecast experiments with the JMA non-hydrostatic model (JMANHM) with grid spacings of 5 and 1.6 km. The experiment with 5-km resolution generated a rainfall band in western Japan that was not reproduced using conventional data, although the rainfall was smaller than observations. The experiment with 1.6-km resolution faithfully reproduced the observed band of intense rainfall.