GFLSZ

Contents

Introduction
Registration form
Obtaining GFs
Superposition of GFs
Description of other data files
Citation policy
Update history

GFLSZ
1. Introduction

We calculated unit response (Green's) functions for elastic deformation due to fault slips in subduction zones of the Japanese Islands based on three-dimensional (3D) finite-element modeling and published here as a Green's function library for subduction zones (GFLSZ). We here targeted two well known subduction zones in Japan, the Nankai Trough subduction zone (NTSZ) and the Japan Trench subduction zone (JTSZ). GFLSZ incorporates 3D heterogeneous elastic property and the ellipsoidal shape of the earth based on an unified seismic velocity structure model proposed for the great portion of the Japanese Islands. Below is the accompanied publication:

*Hori, T., Agata, R., Ichimura, T., Fujita, K., Yamaguchi, T., Iinuma, I.: High Fidelity Elastic Green's Functions for Subduction Zone Models Consistent With the Global Standard Geodetic Reference System. Earth, Planet and Space, 73, 41, 2021. (Open access)

*A Correction to this article was published on 02 April 2021

Please note that we currently provide GFs of surface displacements ("disp") only, not offerring those for surface horizontal strains, volumetric strains and tilts, which are mentioned in the article.

GFLSZ
2. Registration form and contact information

GFLSZ
3. Obtaining GFs

The data sets provided here contain 1km-grid data of GFs for surface displacements and surface volumic strains. We also offer programs to interpolate the values for the points listed in user-defined files for locations of observation points. Here we explain how to perform interpolation and obtain GFs in your target locations, assuming Unix environment. See the table for the file names that corresponds to what you need.

3.1. Download the archive file and extract it. See Table 1 and choose the archive file according to which GFs you need. Move to the parent directory.

3.2. In the parent directory, compile the source code. The compile script uses the GNU Fortran compiler, but you can change the compiler according to your environment.

3.3. Edit or prepare user-defined files for the locations of observation points. The file name is "input/obs_disp.dat" (see the table). The format is common for the four files:

3.4. Execute the program and you will obtain the GF list under the directory "output".

3.5 You will obtained the files output/GF_disp.AAAA.BB.dat, which contain response due to AAAA (0001-0405 for JTSZ and -0459 for NTSZ) th unit slip in the opposite of plate convergence direction for BB=02 and the one perpendicular to it for BB=03. The specific information for the angle is as in the table below:

	BB=02	BB=03
discription	Opposite to the plate convergence direction	Perpendicular to the plate convergence direction
JTSZ	S68.5°E	N21.5°E
NTSZ	S55°E	N35°E

You can use these GFs to construct an observation matrix used in geodetic slip inversion. Output GF data contains surface response in observation points defined in "input/obs_disp.dat". The format is:

time(dummy) uE(m) uN(m) uU(m) FLAG

"FLAG" indicates the level of numerical error included in the GF. For the definition of 1 and 2, see the document on quantification of numerical errors in GFLSZ (ErrorQuantification.pdf and its supporting material provided with the datasets).

0: Numerical errors of GF is sufficiently small.

1: Recommend not to use this point for analyzing nearby events with large magnitude (e.g., 8~9)

2: Recommend not to use this point for analyzing nearby events.

3: The data point is outside the data region for the Japan integrated velocity structure model version 1 (JIVSM) (Koketsu et al. 2009, 2012), which is referred to when creating the numerical simulation model of GFLSZ. GF is not output (99999 is assigned instead)

4: The data point is outside the domain for accurate computation. GF is not output (99999 is assigned instead)

GFLSZ
4. Superposition of GFs

Programs to superimpose GFs and unit slips based on a user-defined slip coefficient data file are provided. First, prepare the slip coefficient data file "input/slipcoef_disp.dat". Every line has two columns in the file, and the i+1 th line in the file is as follows (the first line is a header):

(slip coefficient for 02 direction in the i-th subfault) (slip coefficient for 03 direction in the i-th subfault)

Then run the program that should be already compiled in 3.2.

$python superimpose.py disp

and you will get superimposed surface response (output/superimposed_disp.dat) and slip distribution (output/superimposed_disp_slip.dat).

The format of output/superimposed_disp.dat is the same as in output/GF_disp.AAAA.BB.dat.

The format of output/superimposed_slip_disp.dat is:

Longitude Latitude elevation(m) uE(m) uN(m) uU(m)

Note: You need to complete the preprocess described in Section 3 before carrying out the superposition.

GFLSZ
5. Description of other data files

5.1. Unit fault location: supplements/centerfp_GFLSZ.dat

5.2. Unit fault distribtuion: faultdata/slip.AAAA.BB.csv

5.3 Matrix for the discrete Laplacian operator: supplements/Laplacian.dat

GFLSZ
6. Citation policy

The dataset of GFLSZ provided to users includes surface DEM data extracted from JIVSM. It also includes the data of geoid height interpolated to out target grid from the Earth Gravitational Model 2008 (EGM2008) (Pavlis et al. 2012). Please cite the articles below in Acknowledgements when publishing your work using GFLSZ, as the following:

"The Green's function library for subduction zones by Hori et al. (2021) was used, which was created by JAMSTEC's own modification of a computer program under development by Earthquake Research Institute, The University of Tokyo. The library includes data modified from Japan Integrated Velocity Structure Model version 1 (JIVSM) (Koketsu et al. 2009, 2012) and the Earth Gravitational Model 2008 (Pavlis et al. 2012). "

Hori, T., Agata, R., Ichimura, T., Fujita, K., Yamaguchi, T., Iinuma, I.: High Fidelity Elastic Green's Functions for Subduction Zone Models Consistent With the Global Standard Geodetic Reference System. Earth, Planet and Space, 73, 41, 2021.

Koketsu, K., Miyake, H., Tanaka, Y.: A proposal for a standard procedure of modeling 3-D velocity structures and its application to the Tokyo metropolitan area, Japan. Tectonophysics, 472(1-4), 290-300 (2009). doi: 10.1016/j.tecto.2008.05.037

Koketsu, K., Miyake, H., Suzuki, H.: Japan integrated velocity structure model version 1. Proceedings of the 15th World Conference on Earthquake Engineering (1773) (2012). Lisbon

Pavlis, N.K., Holmes, S.A., Kenyon, S.C., Factor, J.K.: The development and evaluation of the Earth Gravitational Model 2008 (EGM2008). Journal of geophysical research: solid earth 117(B4) (2012). doi: 10.1029/2011JB008916

(Japanese) "東京大学地震研究所が開発中の計算機プログラムをJAMSTECが独自に改変して作成したグリーン関数ライブラリ（Hori et al. 2021）を使用しました。このライブラリには、全国一次地下構造モデル（暫定版）(Koketsu et al. 2009, 2012) と Earth Gravitational Model 2008 (Pavlis et al. 2012) のデータを改変したものが含まれています。"

Input file for obseration point	./input/obs_disp.dat
Command for preprocess	python point_GF.py disp
Output file for preprocess	/output/GF_disp.AAAA.BB.dat
Command for superposition	python superimpose.py disp
Output file for superposition	/output/superimposed_disp.dat, /output/superimposed_disp_slip.dat

Green's function library for subduction zones

GFLSZ1. Introduction

GFLSZ2. Registration form and contact information

GFLSZ3. Obtaining GFs

GFLSZ4. Superposition of GFs

GFLSZ5. Description of other data files

GFLSZ6. Citation policy