Computation of the changes in gravitational gradient components from GRACE observations and analytical model

Fatolazadeh, Farzam; Voosoghi, Behzad; Naeeni, Mehdi Raoofian

doi:10.1007/s40328-015-0152-2

Cited by 3 publications

(3 citation statements)

References 19 publications

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“…It appears better for shallow depth events (less than 15 km), occurring in a magnitude range of 5 to 7. This is consistent with a previous study of Fatolazadeh et al 43 who reported that increasing earthquake depth generates weakened gravity changes. It also explains why the GRACE-based approach did not capture clearly the severe earthquake of magnitude 7.9 and depth of 20 km, which occurred near the Sichuan-Gansu border in 15 th May 2008 in China (Fig.…”

Section: Error Analysissupporting

confidence: 94%

Determination of earthquake epicentres based upon invariant quantities of GRACE strain gravity tensors

Fatolazadeh

Goı̈ta

Azar

2020

Sci Rep

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Investigation of regional and temporal variations in Earth’s gravitational field that are detected by the Gravity Recovery and Climate Experiment (GRACE) twin-satellites may be useful in earthquake epicentre determinations. This study focuses on monthly spherical harmonic coefficients that were extracted from GRACE observations, which were corrected for hydrological effects to determine earthquake epicentres. For the first time, we use the concept of deformation of Earth’s gravity field to estimate invariant components of strain tensors. Four different earthquakes (Iran, China, Turkey, Nepal) were analysed that occurred between 2003 and 2015 and under different hydrological regimes. Wavelet analysis was explored as a means of refining and reconstructing tectonic signals forming the disturbance gravitational potential tensor in the GRACE gravity field models. Dilatation and maximum shear were extracted from these tensors and used to map earthquake epicentre locations. Both components reached their maxima during months of the earthquakes (respectively, 11.78 and 4.93, Bam earthquake; 61.36 and 169.10, Sichuan-Gansu border earthquake; 2415.80 and 627.93, Elazig earthquake; 98.71 and 157.37, Banepa earthquake). For the aforementioned earthquakes, we estimated their respective epicentres in the ranges: φ = 29°–29.5° λ = 58.5°–59°; φ = 32.5°–33° λ = 105.5°–106°; φ = 38.5°–39° λ = 39.5°–40°; and φ = 27.5°–28° λ = 85°–85.5°. Overall, these results agree well with values from other sources. The advance that is provided by our method compared to other research is the ability of determining earthquake epicentres with magnitudes ≤7.5 based upon GRACE observations. However, the approach is of limited use for very deep earthquakes.

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Section: Error Analysissupporting

confidence: 94%

Determination of earthquake epicentres based upon invariant quantities of GRACE strain gravity tensors

Fatolazadeh

Goı̈ta

Azar

2020

Sci Rep

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“…The gravity change due to earthquakes can be expressed by simplified but effective way, in which earthquake is modeled as dislocations on a rectangular plane in a homogeneous elastic half-space [Okubo 1991[Okubo , 1992. Fatolazadeh et. al [2015] developed this formulation in order to compute the gravity gradient changes resulting from earthquake [see also Wang et al, 2012c].…”

Section: Analytical Model Of Co-seismic Gravity Changementioning

confidence: 99%

“…[2016] Improved source parameter estimations for five undersea earthquakes from north component of GRACE gravity and gravity gradient change measurements. Recently, the formulation of Okubo's [1991Okubo's [ , 1992 model has been developed in order to compute the gravitational gradient changes resulting from earthquake [see Fatolazadeh et al, 2015;Wang et al, 2012c]. This analytical model was used to constrain the fault parameters of the 2010 Chile Earthquake using gravimetric observations [Fatolazadeh et al 2017].…”

Section: Introductionmentioning

confidence: 99%

Source Parameter Estimation of Indian Ocean Earthquake from observation of GRACE Gravity Gradient Tensor

Rahimi

Naeeni

2017

Annals of Geophysics

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In this study, the focal mechanism of Indian Ocean earthquake is determined by combination of GRACE gravity gradient change and analytical model of Okubo [1992). To do so, the co-seismic gravity gradient change resulting from Indian Ocean earthquake is derived using monthly solution of GRACE level 02 data after removing the contaminations from hydrological effects and post-seismic creep. Since, De-striping methods lead to reduction and distortion of a co-seismic gravity change signal, it is suggested to compute a set of gravity gradient tensor components e.g. ΔVxx and ΔVxz, because they are more sensitive to small-scale signals and they reduce the striping errors without need to any de-striping filtering. Then the computed gravity gradient components are compared with the gravity gradient components from Okubo model [1992], which accounts the focal mechanism of the earthquake. By the way, the nonlinear inversion algorithm is constructed and solved by Genetic algorithm to find the best values of fault parameters for Indian Ocean earthquake. For better constraining the fault parameters in the inversion process, a sensitivity analysis is also conducted which reveals that the selected model is highly sensitive to a strike angle, dip angle, length, width and average slip, although it is less sensitive to a depth of a fault. The ultimate optimal estimate of the fault parameters shows a good correspondence compared with some existing slip models obtained by various constraints or via inversion of seismic observations.

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Estimation of fault parameters using GRACE observations and analytical model

Fatolazadeh

Naeeni

Voosoghi

et al. 2017

Journal of Geodynamics

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Computation of the changes in gravitational gradient components from GRACE observations and analytical model

Cited by 3 publications

References 19 publications

Determination of earthquake epicentres based upon invariant quantities of GRACE strain gravity tensors

Determination of earthquake epicentres based upon invariant quantities of GRACE strain gravity tensors

Source Parameter Estimation of Indian Ocean Earthquake from observation of GRACE Gravity Gradient Tensor

Estimation of fault parameters using GRACE observations and analytical model

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