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Modern Geomatics Technologies and Applications

Determining the best GRACE-like mission characters to determine the co-
seismic signals

Abolfazl Shahamat, Amir Aminzadeh Ghavifekr
Marand Technical Faculty, University of Tabriz, Tabriz, Iran
a_shahamat@tabrizu.ac.ir

Abstract: The gravity field of the planet earth has temporal variations and our instruments are unfortunately defective
and imperfect to measure that. Therefore, our knowledge of the gravity field of the earth is not complete. After
launching the satellite gravity, gravity data has been collected with remarkable quality. One of the changes that happen
under the surface of the earth is mass movement which occurs as a result of several earthquakes. In the case of using
couple satellites, we would be able to achieve an additional amplification of the gravity signal through inter-satellite
tracking between two low orbiters. In this paper five scenarios are simulated and compared with one another. The
observations made by GRACE and GRACE-FO scenarios have better susceptibility to sense earthquake signals. Even
though it is agreed that, other scenarios may have stronger susceptibility to receive signals. Here, the Maule (2010)
earthquake with 19 degree in strike angle is used as an example. Therefore, the impact of direction of the fault on
detection of coseismic signals supposed that another earthquake occurred in Maule position with exactly the same
specifications but with hypothetical strike angle of 90 degrees. The difference in degree obtained was as a result of
satellite track almost along the perpendicular fault direction. Hence, it is intended to detect whether the fault direction
will produce a different result or not. It is concluded that the GRACE and GRACE-FO are the best scenarios to detect
coseismic signals in this study. All the data used in this paper are the simulated format of Level-1B.
Keywords: GRACE, GRACE-FO; Helix, Pendulum, Cartwheel, Earthquake signal, Gravity changing, Satellite
gravity

1. Introduction

Large earthquakes usually occur close to faults and pose a big threat to communities. Earthquake-
induced gravity changes observed by the researchers can be an indirect way of measuring seismic
deformation. Earthquakes are natural disasters and they can not only be extremely destructive but also
increase the fatality rate. On the other hand, they are good academic sources for scholars of Geodesy,
Geodynamic, Geophysics and Geology to conduct new researches and experiments. This can provide the
scientists with an opportunity of studying the response of the solid earth to tectonic loading. As large
earthquakes end up in massive movements of crust and mantle, the resulting uplifting or subsiding imply
the redistribution of mass and finally cause changes in the gravity field.
Among the researches, study of coseismic deformation is one of the most important subjects. Some
researches have been undertaken to study coseismic deformation in a half-space earth model by Steketee
(1958), Okada (1985) and etc. They have presented analytical views for calculating the surface
displacement, tilt, and strain resulting from various dislocationsSun et al. (2010). Okada (1985) offered a
complete set of analytical formulae to calculate these geodetic deformations by summarizing the previous
studies. Closed-form expressions were also proposed by Okubo (1992) to describe potential and gravity
changes which result from dislocations. Because of their mathematical simplicity, these dislocation
theories have been applied widely to study seismic faults Sun et al. (2010).

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