GSI HOME > Research&Development > Bulletin of GSI > Bulletin of the GSI (Vol.57) > Bulletin of the GSI (Vol.57)  

Bulletin of the GSI (Vol.57)

Takuya NISHIMURA

Abstract

The Niigataken Chuetsu-oki earthquake in 2007 occurred just west of the coast of Kashiwazaki in Niigata Prefecture, central Japan on July 16, 2007. We present an overview of crustal deformation and fault models associated with the earthquake by reviewing three published papers by a group of the Geographical Survey Institute. The permanent GPS network (GEONET), interferometric analysis of SAR acquired by “Daichi” satellite (ALOS), and leveling clarify coseismic deformation in detail. Although it is difficult to determine which plane in two conjugate planes of the focal solution ruptured only from the geodetic data on land, a combination of a large southeast-dipping fault and a small northwest-dipping fault successfully explain the observed deformation and the aftershock distribution. The southeast-dipping fault is found to have released a seismic moment that is four times that released by the northwest-dipping conjugate fault. The interferograms reveal not only a large deformation near the source area of the earthquake but also a local uplift in the region of active folding, 15 km east of the earthquake epicenter. The 1.5-km-wide and 15-km-long band of uplift is located along the anticline axis of an active fold and cannot be explained by the elastic deformation resulting from the mainshock of the earthquake. This uplift suggests the episodic growth of active folds.

Contents

1. Introduction

2. Geodetic Data

 2.1 GPS

 2.2 InSAR

 2.3 Leveling

3. Coseismic fault model

4. Episodic growth of active

5. Concluding remarks

Acknowledgement

References



Hiroshi MUNEKANE, Yuki KUROISHI, Yuki HATANAKA, KazuhiroTAKASHIMA, Masayoshi ISHIMOTO and Mikio TOBITA

Abstract

We installed a GPS station in the premises of the Geographical Survey Institute in Tsukuba. The station is directly attached to the inner tube of a subsidence observation well, anchored at a depth of 190 m, so that it is less affected by seasonal elastic deformations of shallow soils due to groundwater extraction for irrigation. We evaluated the quality of the station by comparing the GPS-derived vertical displacements with those from two independent measurements; subsidence-meter and leveling. For comparison, we prepared two sets of GPS solutions with different analysis strategies; 1) short-distance strategy: where we analyze GPS carrier-phases on L1 and L2 frequencies independently to estimate baseline components only, and 2) long-distance strategy: where we analyze ionosphere-free combinations of GPS carrier-phases on L1 and L2 frequencies to estimate tropospheric delays as well as baseline components. We found that while the GPS-derived vertical displacements in the short-distance strategy generally agree with those from the independent measurements, those in the long-distance strategy systematically disagree. We also noticed that the GPS-derived vertical displacements in both strategies have noticeable common errors in winter. We found that the disagreement of the displacements in the short-distance strategy are errors caused by the multipath from the surface of the roof of the room housing the subsidence observation well, and the latter errors are caused by water droplets formed inside the radome because of water condensation in the room’s air in winter. These errors should be mitigated before this station can be utilized as a reliable reference station.

Contents

1. Introduction

2. Outline of the GPS station

3. Comparison of the GPS-derived vertical displacements with independent measurements

4. Investigation of error sources of the GPS-derived vertical displacements

 4.1 Errors of the GPS-derived vertical displacements in the long-distance strategy

 4.2 Errors of the GPS-derived vertical displacements in winter

5. Concluding remarks

Acknowledgments

References



Isabelle PANET, Yuki KUROISHI and Matthias HOLSCHNEIDER

Abstract

Knowing the geoid over Japan is essential for many geodetical and geophysical applications. Because of the tectonic settings of the area, significant geoid undulations occur in a wide range of spatial scales and make the determination of the geoid a complex task. In some applications, high absolute accuracy at long and medium wavelengths is required for geoid models with high resolution, which can be achieved by a proper combination of satellite gravity information with densely-distributed surface gravity data after careful consideration of their respective error characteristics. Here we show how to realize such a combination in a flexible way using spherical wavelets. The gravity potential is expressed as a linear combination of wavelets, whose coefficients are obtained by a least squares adjustment of the datasets. The combination needs to handle a large system of equations and we apply a domain decomposition method. First, we define sub-domains as subsets of wavelets. Based on the localization properties of the wavelets in space and frequency, we define hierarchical sub-domains of wavelets at different scales. On each scale, blocks of sub-domains are defined by using a tailored spatial splitting of the area. Second, we approximate the normal matrix for each block by introducing local approximation of the wavelets depending on the scale, in which local averages of the data are actually used for computation. Finally, we solve the system iteratively. In the beginning we validate the method with synthetic data, considering two kinds of noise: white noise and colored noise. We then apply the method to data over Japan: a satellite-based geopotential model, EIGEN-GL04S, and a local gravity model from a combination of land and marine gravity data and an altimetry-derived marine gravity model. A hybrid spherical harmonics/wavelet model of the geoid is obtained at about 15 km resolution and the residuals indicate the existence of possible biases in the surface model. This information is used to correct the local model and the method is repeated with the corrected data, resulting in an improved hybrid model of the gravity field over Japan.

Contents

1. Introduction

2. Wavelet representation of the gravity field

 2.1 Wavelet frames

 2.2 Consideration for application to local gravity field modeling

 2.3 Computation of wavelet coefficients

3. Domain decomposition methods

 3.1 Definition of the sub-domains

 3.2 Principle of the Schwarz algorithms

 3.3 Approximations of the sub-domain normals

 3.4 Scale-dependent reweighting to data

 3.5 The regularization

4. Validation with synthetic data

 4.1 White noise case

 4.2 Colored noise case

5. Application over Japan

6. Conclusion

References



Shinobu KURIHARA and Kensuke KOKADO

Abstract

Very Long Baseline Interferometry (VLBI) is a space geodetic technique by which Earth orientation parameters (EOP) can be measured. The Tsukuba 32-m VLBI station of the Geographical Survey Institute has been involved in intensive VLBI sessions scheduled by the International VLBI service for Geodesy and Astrometry (IVS) every weekend for measuring the UT1(Universal Time 1), which is an element of an EOP series. In recent years, the latency of UT1 measurement performed by VLBI has been reduced by adopting electronic VLBI (e-VLBI) technology. At the Tsukuba 32-m station, an ultra-rapid UT1 experiment has been performed in collaboration with the Kashima, Onsala, and Metsähovi VLBI stations since 2007 to obtain UT1 results within 30 min of the end of observation sessions. We have shortened the latency of UT1 measurement by carrying out real-time data transfer, automatic data conversion, and correlation processing during the observation session, and we succeeded in obtaining the UT1 result 3 min 45 sec after the end of the session. We plan to introduce the newly developed technology in regular intensive VLBI sessions and 24-h VLBI sessions, and we aim to obtain the UT1 results within 30 min of the end of the session. It is expected that our technique can help improve the accuracy of UT1 data published by the International Earth Rotation and Reference Systems Service (IERS).

Contents

1. Introduction

2. Current UT1 measurements

 2.1 UT1 measurements and predicted UT1 value

 2.2 IVS Intensive Sessions

3. Details of the e-VLBI technique

4. Ultra-rapid UT1 experiment

 4.1 Specifications of VLBI stations involved in experiments

 4.2 Observation scheduling

 4.3 Data-transfer and processing systems

 4.4 Automatic analysis program

5. Results of the ultra-rapid UT1 experiments

 5.1 Details of each UT1 experiment

 5.2 Accuracy of UT1 measurement

6. Future plans

 6.1 Increasing data rate in Ultra-rapid experiment

 6.2 Ultra-rapid observation in regular observations

7. Conclusions

References



Noriko KISHIMOTO, Yoshikazu FUKUSHIMA, Tsuneo TANAKA, Takayuki NAKAMURA, Kosei OTOI, Hidehisa TAKAHASHI, Seiichi OOMIYA, Shuhei KOJIMA and Masayuki YOSHIKAWA

Abstract

Global Map Version 1 was released in 2008 and Global Map Version 2 will be released by 2013, developed by respective National Mapping Organizations of the world. In order to promote application and distribution of Global Map data, revision of Global Map Specifications, such as 1) modification of Data Dictionary, 2) adoption of GML as vector data, 3) change in data tiling, and 4) correspondence of metadata with International Standard has been made.

This paper reports the revision process, major points discussed at the “International Workshop on the Revision of Specifications for Global Map Version 2” in September 2009, and future prospects of Global Mapping Project from a viewpoint of the revision of Specifications.

Contents

1. Introduction

2. Process of Revision

 2.1 Outline of the process

 2.2 Details of the process

3. Revision Points

 3.1 Basic Policies of Revision

 3.2 Outline of the revision points

 3.3 Data Dictionary

  3.3.1 General

  3.3.2 Transportation

  3.3.3 Boundaries

  3.3.4 Drainage

  3.3.5 Population Centres

 3.4 Vector Data Format

  3.4.1 Problems of VPF formats

  3.4.2 Outline and merit of GML

  3.4.3 History and Points of Discussion

  3.4.4 GML for Global Map

 3.5 Area of File Coverage (Tiling)

  3.5.1 Current file coverage and its problems

  3.5.2 Criteria of Dividing Data

  3.5.3 Revised file of coverage

 3.6 Metadata

  3.6.1 Needs for Revising Metadata Specifications

  3.6.2 Compliance with ISO 19115

4. Future Prospects

Acknowledgement

Reference


Appendix

A. History on the Revision of Global Map Specifications

B. Discussion at ISCGM toward the Revision of Specifications for Global Map Version 2

C. Agenda of Open Forum in International Workshop on the Revision of Specifications for Global Map Version 2

D. International Workshop on the Revision of Specifications for Global Map Version 2, 8th - 10th September 2009, Summary

E. GML Schema and GML sample data


Geospatial Information Planning Office, Planning Department

Abstract

With respect to policies concerning Advancement of Utilizing Geospatial Information (AUGI), the Basic Act on the Advancement of Utilizing Geospatial Information (hereafter, “Basic Act”), which defines basic elements for AUGI policies, came into effect in August 2007 while establishing basic principles and clarifying the responsibilities of both the national and local governments. In addition, the Basic Act provides that a basic plan concerning AUGI is to be formulated. This led to the discussion by the Committee on Geographic Information System and Positioning, subsequently followed by the April 2008 cabinet decision, of the Basic Plan for the Advancement of Utilizing Geospatial Information (hereafter, “Basic Plan”).

The Basic Plan sets the period of this plan to be until FY2011. Through the use of Geographic Information System (GIS) and Space-based Positioning, Navigation and Timing (Space-based PNT), it also aims to create an advanced geospatial information utilization society where people are able to utilize the geospatial information anytime, anywhere and to obtain accurate information derived from highly sophisticated analyses for their activities.

Policies of the Geographical Survey Institute (GSI) on the Basic Plan being encompassed are: surveys and research for formulating rules related to the general development, updating, provision and distribution of geospatial information; promotion of the standardization of geospatial information; and development and updating of Fundamental Geospatial Data (FGD).

Regarding all the governmental policies including the said policies, the Committee on Geographic Information System and Positioning (Chair: Assistant Chief Cabinet Secretary) established the Action Plan for the Advancement of Utilizing Geospatial Information (G-Spatial Action Plan) in August 2008 and is conducting a follow-up on the state of policy progress each year.

Contents

1. Introduction

2. Basic Plan Overview

 2.1 Plan Overview

 2.2 Goal to be Achieved – Realization of an Advanced Geospatial Information Utilization Society

 2.3 Table of Contents of the Basic Plan

 2.4 Important Points for the Implementation

  2.4.1 Preparing draft guidelines related to the development, provision and distribution of geospatial information and promoting the provision and distribution of it

  2.4.2 Promoting the development and provision of FGD

  2.4.3 Promoting the establishment and utilization of a high-tech base for Space-based PNT

  2.4.4 Strengthening ties among business, academia and government as they relate to the utilization of geospatial information

 2.5 Consistency with the Basic Plan on Ocean Policy

 2.6 Formulation of G-Spatial Action Plan

3. Measures of the Geographical Survey Institute on the Basic Plan

 3.1 General Measures

  3.1.1 Developing institutional arrangements of relevant organizations and strengthening their alliances

  3.1.2 Implementation of surveys and research

  3.1.3 Dissemination of knowledge

  3.1.4 Nurturing human resources

  3.1.5 Promotion of international cooperation

 3.2 Measures Related to Geographic Information System (GIS)

  3.2.1 Establishing and disseminating standards, etc., related to the development and provision of geospatial information

  3.2.2 Promoting the development and provision of geospatial information

 3.3 Policies Related to Space-Based PNT

  3.3.1 International cooperation regarding Space-based PNT

  3.3.2 Promotion of the Quasi-Zenith Satellite System project

  3.3.3 Provision of information for utilizing Space-based PNT

4. Conclusion

References


Go to top