A splash in Earth gravity from the 2004 Sumatra Earthquake

Sabadini, R.; Via, G. Dalla; Hoogland, Masja; Aoudia, Abdelkrim

doi:10.1029/2005eo150001

Cited by 7 publications

(16 citation statements)

References 6 publications

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“…Some studies have also used models to explain the GRACE observations, e.g. [10,5,22]. The last two modelled the solid earth only geoid height change as a dipole with a more prominent positive anomaly than negative anomaly, but as already mentioned de Linage et al [5] used a zeroth order approximation of the ocean effect and so obtained a more prominent negative pole.…”

Section: Comparison With Gracementioning

confidence: 99%

“…This effect increases with smaller dip angles because then the horizontal shift for sources increases, requiring a smaller spacing between the subsequent sources to obtain convergence. For clarity of the figure less point sources per unit depth are In literature, next to detailed slip models, models consisting of only a few point sources [13] and models with homogenous distribution of slip with depth [22,15] have been used to model co-seismic vertical deformation or geoid changes. Therefore, to investigate the relevance of a realistic distribution of slip with depth we show in figure 2 the vertical deformation at the surface and the geoid height change due to three different 2D moment distributions as well as due to a single source at half the depth of the fault plane.…”

Section: Co-seismic Solid Earth Model For a Shallow Earthquakementioning

confidence: 99%

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Ocean contribution to co-seismic crustal deformation and geoid anomalies: Application to the 2004 December 26 Sumatra–Andaman earthquake

Broerse

Vermeersen

Riva

et al. 2011

Earth and Planetary Science Letters

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Large earthquakes do not only heavily deform the crust in the vicinity of the fault, they also change the gravity field of the area affected by the earthquake due to mass redistribution in the upper layers of the Earth. Besides that, for sub-oceanic earthquakes deformation of the ocean floor causes relative sea level changes and mass redistribution of water that have again a significant effect on the gravity field. To model these deformations, sea level changes and gravity field perturbations self-consistently we use an adapted version of the sea level equation (SLE) that has been used for glacial isostatic adjustment studies. The sea level equation, next to our normal mode model for seismic solid earth modelling, allows us to compute a gravitationally self-consistent solution for the co-seismic relative sea level, surface deformation and geoid height changes. We apply our geographically detailed models to the case of the 2004 December 26 Sumatra-Andaman earthquake. Recent studies that have modelled the ocean mass effect on co-seismic gravity change for this specific earthquake show model results that indicate a broad negative change in geoid height around the fault due to ocean water redistribution [5], [13]. Our model results for the ocean contribution to geoid height differ from these studies in the sense that we find a pattern similar to the elongated dipole pattern of the solid earth model outputs for gravity and vertical deformation, together with a relatively small broad negative geoid height change. We explain the relation between outcomes for geoid height, relative sea level and vertical deformation of the ocean floor and we confront our model results with a least squares estimation of the co-seismic discontinuity in GRACE-derived gravity field time series. We show that taking into account the contribution of ocean water redistribution to the co-seismic geoid height change next to a compressible solid earth model is essential to explain the predominant negative co-seismic geoid anomalies from the GRACE gravity field solutions. Besides, we introduce a detailed approach to modelling an earthquake in a normal mode model that better approximates realistic continuous slip on the fault plane than models that do not distribute slip with depth. To demonstrate the importance of the slip distribution we show the differences in outcomes for modelled geoid height and vertical deformation.

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Section: Comparison With Gracementioning

confidence: 99%

Section: Co-seismic Solid Earth Model For a Shallow Earthquakementioning

confidence: 99%

Ocean contribution to co-seismic crustal deformation and geoid anomalies: Application to the 2004 December 26 Sumatra–Andaman earthquake

Broerse

Vermeersen

Riva

et al. 2011

Earth and Planetary Science Letters

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“…Co‐seismic gravitational perturbations are visible from gravity space mission data [ Mikhailov et al , 2004; Sabadini et al , 2005; Han et al , 2006; de Linage et al , 2009]. We herein analyze co‐seismic geoid and gravity anomalies from the 2004 Sumatran earthquake by means of a new, compressible self‐gravitating Earth model, that is fully realistic as it builds on PREM [ Dziewonski and Anderson , 1981] and represents the elastic limit of viscoelastic models, recently used for post‐glacial rebound studies [ Cambiotti et al , 2010] and developed for co‐seismic studies by Smylie and Mansinha [1971] and Sun and Okubo [1993].…”

Section: Introductionmentioning

confidence: 99%

GRACE gravity data help constraining seismic models of the 2004 Sumatran earthquake

et al. 2011

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The analysis of Gravity Recovery and Climate Experiment (GRACE) Level 2 data time series from the Center for Space Research (CSR) and GeoForschungsZentrum (GFZ) allows us to extract a new estimate of the co‐seismic gravity signal due to the 2004 Sumatran earthquake. Owing to compressible self‐gravitating Earth models, including sea level feedback in a new self‐consistent way and designed to compute gravitational perturbations due to volume changes separately, we are able to prove that the asymmetry in the co‐seismic gravity pattern, in which the north–eastern negative anomaly is twice as large as the south–western positive anomaly, is not due to the previously overestimated dilatation in the crust. The overestimate was due to a large dilatation localized at the fault discontinuity, the gravitational effect of which is compensated by an opposite contribution from topography due to the uplifted crust. After this localized dilatation is removed, we instead predict compression in the footwall and dilatation in the hanging wall. The overall anomaly is then mainly due to the additional gravitational effects of the ocean after water is displaced away from the uplifted crust, as first indicated by de Linage et al. (2009). We also detail the differences between compressible and incompressible material properties. By focusing on the most robust estimates from GRACE data, consisting of the peak‐to‐peak gravity anomaly and an asymmetry coefficient, that is given by the ratio of the negative gravity anomaly over the positive anomaly, we show that they are quite sensitive to seismic source depths and dip angles. This allows us to exploit space gravity data for the first time to help constraining centroid‐momentum‐tensor (CMT) source analyses of the 2004 Sumatran earthquake and to conclude that the seismic moment has been released mainly in the lower crust rather than the lithospheric mantle. Thus, GRACE data and CMT source analyses, as well as geodetic slip distributions aided by GPS, complement each other for a robust inference of the seismic source of large earthquakes. Particular care is devoted to the spatial filtering of the gravity anomalies estimated both from observations and models to make their comparison significant.

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“…A geoid height change due to the earthquake could reach at 1.5 cm. Sabadini and Dalla (2005) estimated the peak-to-peak change of the geoid undulation caused by the 2004 Sumatra earthquake to 1.8 cm. Such gravity and geoid height changes are expected to be detectable by modern space techniques, such as satellite radar altimetry and gravity missions.…”

Section: Introductionmentioning

confidence: 99%

Impact of a precise geoid model in studying tectonic structures—A case study in Iran

Kiamehr

Sjöberg

2006

Journal of Geodynamics

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A splash in Earth gravity from the 2004 Sumatra Earthquake

Cited by 7 publications

References 6 publications

Ocean contribution to co-seismic crustal deformation and geoid anomalies: Application to the 2004 December 26 Sumatra–Andaman earthquake

Ocean contribution to co-seismic crustal deformation and geoid anomalies: Application to the 2004 December 26 Sumatra–Andaman earthquake

GRACE gravity data help constraining seismic models of the 2004 Sumatran earthquake

Impact of a precise geoid model in studying tectonic structures—A case study in Iran

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