scholarly journals High-fidelity elastic Green’s functions for subduction zone models consistent with the global standard geodetic reference system

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Takane Hori ◽  
Ryoichiro Agata ◽  
Tsuyoshi Ichimura ◽  
Kohei Fujita ◽  
Takuma Yamaguchi ◽  
...  
Keyword(s):  
Reference System ◽  
Subduction Zones ◽  
Structural Models ◽  
Tsunami Hazard ◽  
Geodetic Reference System ◽  
High Fidelity ◽  
Ellipsoidal Shape ◽  
The Earth ◽  
Hazard Assessments ◽  
Realistic Topography

AbstractGreen’s functions (GFs) for elastic deformation due to unit slip on the fault plane comprise an essential tool for estimating earthquake rupture and underground preparation processes. These estimation results are often applied to generate important information for public such as seismic and tsunami hazard assessments. So, it is important to minimize the distortion of the estimation results on the numerical models used for calculating GFs to guarantee assessment reliability. For this purpose, we here calculated GFs based on a numerical model that is of high fidelity to obtain realistic topography and subsurface structural models of the Earth. We targeted two well-known subduction zones in Japan, the Nankai Trough and the Japan Trench. For these subduction zones, databases for realistic topography and subsurface structural models of the Earth are available in the “Japan integrated velocity structure model version 1”, which was proposed for earthquake hazard assessments conducted by the Japanese government. Furthermore, we eliminated the inconsistency in processing calculated GFs and space geodetic observation data for surface displacements, which is often overlooked, by using the same coordinate system. The ellipsoidal shape of the Earth, which is often approximated with a projected plane or a spherical shape, was also incorporated by faithfully following the definitions of the coordinate systems in Geodetic Reference System 1980, which is the global standard for space geodesy. To calculate elastic GFs based on such high-fidelity subduction zone databases with the ellipsoidal shape of the Earth, we introduced the finite element (FE) method. In the FE meshes, the resolution of the topography and subsurface structure is the same as that of the original databases. Recent development of the state-of-the-art computation techniques for the rapid calculation of crustal deformation using large-scale FE models allows for GF calculation based on such a high-fidelity model. However, it is generally not easy to perform such calculations. Thus, we released a library for the GFs calculated with 1-km grid spacing on the ground surface in this study to the geoscience community on a web server, aiming to contribute more reliable seismic and tsunami hazard assessment.

scholarly journals High Delity Elastic Green's Functions for Subduction Zone Models Consistent With the Global Standard Geodetic Reference System

2020 ◽  
Author(s):  
Takane Hori ◽  
Ryoichiro Agata ◽  
Tsuyoshi Ichimura ◽  
Kohei Fujita ◽  
Takuma Yamaguchi ◽  
...  
Keyword(s):  
Reference System ◽  
Subduction Zones ◽  
Structural Models ◽  
Tsunami Hazard ◽  
Geodetic Reference System ◽  
Coordinate Systems ◽  
Ellipsoidal Shape ◽  
The Earth ◽  
Hazard Assessments ◽  
Realistic Topography

Abstract Green's functions (GFs) for elastic deformation due to unit slip on the fault plane comprise an essential tool for estimating earthquake rupture and underground preparation processes. These estimation results are often applied to generate important information for public such as seismic and tsunami hazard assessments. So, it is important to minimize the distortion of the estimation results on the numerical models used for calculating GFs to guarantee assessment reliability. For this purpose, we here calculated GFs based on a numerical model that is of high delity to obtain realistic topography and subsurface structural models of the Earth. We targeted two well-known subduction zones in Japan, the Nankai Trough and the Japan Trench. For these subduction zones, databases for realistic topography and subsurface structural models of the Earth are available in the \Japan integrated velocity structure model version 1", which was proposed for earthquake hazard assessments conducted by the Japanese government.Furthermore, in order to eliminate inconsistencies in data processing of the calculated and observed response, we used the same coordinate systems for processing GFs as those adopted widely to process space geodetic observation data for surface displacements. The ellipsoidal shape of the Earth, which is often approximated with a projected plane or a spherical shape, was also incorporated by faithfully following the denitions of the coordinate systems in Geodetic Reference System 1980, which is the global standard for space geodesy. To calculate elastic GFs based on such high delity subduction zone databases with the ellipsoidal shape of the Earth, we introduced the nite element (FE) method. In the FE meshes, the resolution of the topography and subsurface structure is the same as that of the original databases. Recent development of the state-of-the-art computation techniques for the rapid calculation of crustal deformation using large-scale FE models allows for GF calculation based on such a high delity model. However, it is generally not easy to perform such calculations. Thus, we released a library for the GFs calculated in this study to the geoscience community on a web server, aiming to contribute more reliable seismic and tsunami hazard assessment.

scholarly journals Correction to: High-fidelity elastic Green’s functions for subduction zone models consistent with the global standard geodetic reference system

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Takane Hori ◽  
Ryoichiro Agata ◽  
Tsuyoshi Ichimura ◽  
Kohei Fujita ◽  
Takuma Yamaguchi ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Reference System ◽  
Green's Functions ◽  
Green’S Functions ◽  
Geodetic Reference System ◽  
High Fidelity

An amendment to this paper has been published and can be accessed via the original article.

scholarly journals The 1964 IAU System and the Geodetic Reference System 1967

1971 ◽  
Vol 9 ◽  
pp. 279-280
Author(s):  
J. Kovalevsky
Keyword(s):  
Gravitational Field ◽  
Reference System ◽  
Geodetic Reference System ◽  
The Earth

In 1964, the IAU adopted, among the primary constants of its system, the following three constants especially related to the shape, dimensions and gravitational field of the Earth:a = 6378160 mGM = 398603 × 109m3/s2J2 = 0.0010827These values were discussed in 1967 by the IAG and adopted by the IUGG as the basis of a ‘Geodetic Reference System 1967’. Although at that time better values of these constants were available, IUGG decided to adopt the values of the IAU system in order to keep consistency with the values agreed upon by the astronomers.

The Terrestrial Coordinate System and International Earth-rotation Services

1985 ◽  
Vol 38 (02) ◽  
pp. 216-217
Author(s):  
G. A. Wilkins
Keyword(s):  
Coordinate System ◽  
Earth Rotation ◽  
Reference System ◽  
New Techniques ◽  
Crustal Movements ◽  
Earth Observations ◽  
The Earth ◽  
External Reference ◽  
External Objects ◽  
Rotation Of The Earth

New techniques of measurement make it possible in 1984 to determine positions on the surface of the Earth to a much higher precision than was possible in 1884. If we look beyond the requirements of navigation we can see useful applications of global geodetic positioning to centimetric accuracy for such purposes as the control of mapping and the study of crustal movements. These new techniques depend upon observations of external objects, such as satellites or quasars rather than stars, and they require that the positions of these objects and the orientation of the surface of the Earth are both known with respect to an appropriate external reference system that is ‘fixed’ in space. We need networks of observing stations and analysis centres that monitor the motions of the external objects and the rotation of the Earth. Observations of stars by a transit circle are no longer adequate for this purpose.

A multi-scenario assessment of the seismogenic tsunami hazard for Bangladesh

2019 ◽  
Vol 11 (2) ◽  
pp. 156-168
Author(s):  
Janaka J. Wijetunge
Keyword(s):  
Subduction Zones ◽  
Submarine Canyon ◽  
Tsunami Hazard ◽  
Seismic Zone ◽  
Tsunami Propagation ◽  
Content Type ◽  
Arrival Times ◽  
Tsunami Waves ◽  
Scenario Assessment ◽  
Seismic Scenarios

Purpose This paper aims to describe a multi-scenario assessment of the seismogenic tsunami hazard for Bangladesh from active subduction zones in the Indian Ocean region. Two segments of the Sunda arc, namely, Andaman and Arakan, appear to pose a tsunamigenic seismic threat to Bangladesh. Design/methodology/approach High-resolution numerical simulations of tsunami propagation toward the coast of Bangladesh have been carried out for eight plausible seismic scenarios in Andaman and Arakan subduction zones. The numerical results have been analyzed to obtain the spatial variation of the maximum tsunami amplitudes as well as tsunami arrival times for the entire coastline of Bangladesh. Findings The results suggest that the tsunami heights are amplified on either side of the axis of the submarine canyon which approaches the nearshore sea off Barisal in the seaboard off Sundarban–Barisal–Sandwip. Moreover, the computed tsunami amplitudes are comparatively higher north of the latitude 21.5o in the Teknaf–Chittagong coastline. The calculated arrival times indicate that the tsunami waves reach the western half of the Sundarban–Barisal–Sandwip coastline sooner, while shallow water off the eastern half results in a longer arrival time for that part of the coastline, in the event of an earthquake in the Andaman seismic zone. On the other hand, most parts of the Chittagong–Teknaf coastline would receive tsunami waves almost immediately after an earthquake in the northern segment of the Arakan seismic zone. Originality/value The present assessment includes probabilistic measures of the tsunami hazard by incorporating several probable seismic scenarios corresponding to recurrence intervals ranging from 25 years to over 1,000 years.

scholarly journals UNCERTAINTY OF BATHYMETRY MODELS AND EFFECT ON TSUNAMI MODELS

2020 ◽  
pp. 22
Author(s):  
Ignacio Sepulveda ◽  
Jennifer S. Haase ◽  
Philip L.-F. Liu ◽  
Mircea Grigoriu ◽  
Brook Tozer ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Random Field ◽  
Field Model ◽  
Tsunami Hazard ◽  
Response Uncertainty ◽  
Random Field Model ◽  
Three Stages ◽  
Hazard Assessments ◽  
The Impact

We describe the uncertainties of altimetry-predicted bathymetry models and then quantify the impact of this uncertainty in tsunami hazard assessments. The study consists of three stages. First, we study the statistics of errors of altimetry-predicted bathymetry models. Second, we employ these statistics to propose a random field model for errors anywhere. Third, we use bathymetry samples to conduct a Monte Carlo simulation and describe the tsunami response uncertainty. We found that bathymetry uncertainties have a greater impact in shallow areas. We also noted that tsunami leading waves are less affected by uncertainties.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/zzL_XWWAQ7o

scholarly journals Precession and Nutations of Mars calculated with Kinoshita’s Model

1997 ◽  
Vol 165 ◽  
pp. 325-330 ◽  
Author(s):  
S. Bouquillon ◽  
J. Souchay
Keyword(s):  
Reference System ◽  
Theoretical Study ◽  
The Sun ◽  
Canonical Variables ◽  
The Earth

AbstractThis paper presents the theoretical study of precession and nutation of Mars in a rigourous way. For this work we choose a natural reference system, based on the concept of non-rotating origin, and the appropriate canonical variables. Then, we solve the equations of the problem by taking into account the effects of the Sun, the Earth, Jupiter, and satellites of Mars, Phobos and Deimos.

scholarly journals The Reference Frame Determined From the Observation of Minor Planets by Hipparcos

1990 ◽  
Vol 141 ◽  
pp. 329-336
Author(s):  
B. Morando ◽  
A. Bec-Borsenberger
Keyword(s):  
Reference Frame ◽  
High Precision ◽  
Reference System ◽  
Initial Position ◽  
Minor Planet ◽  
Minor Planets ◽  
The Moon ◽  
Phase Effect ◽  
The Earth ◽  
A Minor

The observation of minor planets by Hipparcos offers the opportunity to obtain high precision positions for some minor planets. About fifty minor planets are on the programme. Their ephemerides had to be improved in order to reach a precision of 1 arsec and occultations by the Earth and the Moon had to be predicted.From the position of a minor planet on reference great circles at different times better values of the initial position and velocity will be deduced but the reduction of the observations of the minor planets have to take into account the displacement of the photocentre relative to the centre which is due to the shape, the phase effect and the scattering properties of the surface. For some very small planets considered as star like this diplacement will be small and the precise positions obtained will allow to position the dynamical reference system relative to the Hipparcos system. For the bigger minor planets the observations by Hipparcos may give informations on the shape and scattering properties of the surface.

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