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We perform an extensive analysis of the low-degree gravity field harmonics measured by the GRACE mission, in order to find a signature of the postseismic relaxation following the 2004 Sumatra earthquake. We find a statistically... more
We perform an extensive analysis of the low-degree gravity field harmonics measured by the GRACE mission, in order to find a signature of the postseismic relaxation following the 2004 Sumatra earthquake. We find a statistically significant perturbation in the secular trend of low-degree zonal coefficients (Jl) in correspondence of the 2004 Sumatra earthquake and a similar perturbation, but with weak associated statistical significance, also in the nonzonal coefficients. Technical features and results of such analysis are discussed. The time-dependent postseismic evolution of harmonic coefficients is modeled for various asthenosphere viscosity values, using a theoretical model of global postseismic deformation. The observed change in secular trend is found to be consistent with our modeling results but it cannot be used to discriminate between viscosities. A forward modeling of the perturbations to time-dependent zonal variation rates following the Sumatra earthquake for various asthenospheric viscosities is provided. As a result, an evident signature of the Sumatra earthquake on $\dot{J}$l time series is expected for asthenospheric viscosity values below 1018 Pa s. Therefore, long term $\dot{J}$l time histories from satellite laser ranging will be able to put constraints on the asthenosphere viscosity, if such a signature is evidenced from data or, at least, put lower limits if no significant perturbation will be observed.
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A spherically symmetric Earth model with viscoelastic rheology is used to study the postseismic rebound associated with finite lithospheric dislocations. We perform a systematic study of surface deformations due to sources characterized... more
A spherically symmetric Earth model with viscoelastic rheology is used to study the postseismic rebound associated with finite lithospheric dislocations. We perform a systematic study of surface deformations due to sources characterized by two- and three-dimensional faults, modeled by a linear and planar distribution of point sources. Our approach is based on the normal mode technique for a layered Earth
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One of the most recent novelties in volcanology is the finding of a statistically significant influence of remote strong earthquakes on the largest explosive eruptions of the last century. Here, we model such interaction in terms of the... more
One of the most recent novelties in volcanology is the finding of a statistically significant influence of remote strong earthquakes on the largest explosive eruptions of the last century. Here, we model such interaction in terms of the coseismic and postseismic stress diffusion. The stress variation consists of the elastic response of the lithosphere, and the viscoelastic relaxation of the
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... Abstract. Estimating Lateral Structure in the Earth’s Outer Core. Estimating Lateral Structure in the Earth’s Outer Core. Antonio Piersanti. ...
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By means of a spherical Earth model with Maxwell rheology, an analysis of the postseismic deformation field due to the viscoelastic relaxation of the mantle and asthenosphere following the great 1960 Chile earthquake is performed. Due to... more
By means of a spherical Earth model with Maxwell rheology, an analysis of the postseismic deformation field due to the viscoelastic relaxation of the mantle and asthenosphere following the great 1960 Chile earthquake is performed. Due to the exceptional energy release of that earthquake, geomorphological evidences of postseismic deformation are available in a broad area surrounding the rupture zone. The comparison of the synthetic results with the available data allows to put some constraints on the viscosity of the asthenosphere beneath the Chilean region. Values between 8.1019 and 1020Pas are compatible with the available postseismic deformation field data.
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Large earthquakes are a potentially important source of relative sea level variations, since they can drive global deformation and simultaneously perturb the gravity field of the Earth. For the first time, we formalize a gravitationally... more
Large earthquakes are a potentially important source of relative sea level variations, since they can drive global deformation and simultaneously perturb the gravity field of the Earth. For the first time, we formalize a gravitationally self-consistent, integral sea level equation suitable for earthquakes, in which we account both for direct effects by the seismic dislocation and for the feedback from
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The post-seismic response of a viscoelastic Earth to a seismic dislocation can be computed analytically within the framework of normal-modes, based on the application of propagator methods. This technique, widely documented in the... more
The post-seismic response of a viscoelastic Earth to a seismic dislocation can be computed analytically within the framework of normal-modes, based on the application of propagator methods. This technique, widely documented in the literature, suffers from several shortcomings; the main drawback is related to the numerical solution of the secular equation, whose degree increases linearly with the number of viscoelastic
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... of 3 cm yr −1 with respect to the African shore of Gulf of Suez, in absence of significantcontemporary seismic activity ... 4. Modeling approach. ... This conclusion, translated in terms of strain, implies that low displacement... more
... of 3 cm yr −1 with respect to the African shore of Gulf of Suez, in absence of significantcontemporary seismic activity ... 4. Modeling approach. ... This conclusion, translated in terms of strain, implies that low displacement gradients should be observed in the thicker continental crust of ...
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We investigated the plausibility of remote fault triggering on a global scale as a result of postseismic stress transfer by large earthquakes. Previous studies have shown that the postseismic stress field generated by eight of the largest... more
We investigated the plausibility of remote fault triggering on a global scale as a result of postseismic stress transfer by large earthquakes. Previous studies have shown that the postseismic stress field generated by eight of the largest events that have occurred in the Pacific area promoted the rupture of 53.6% of all the M≥5 events recorded in the last century in the circumpacific ring. We tried to assess the statistical significance of this result by performing a set of new statistical simulations involving very intensive computational tasks. To this aim we implemented a new numerical procedure based on parallel codes. We found that our simulations did not show strong statistical evidence, but there was a clear indication that as we applied more realistic geometrical constraints to the synthetic distributions, we tended to reproduce more closely the observed quantities. These results support the hypothesis of some kind of physical connection of the configuration of a plate margin and its activity with those of all the other plate margins, more than the possibility of remote fault interaction in the ‘classical’ sense.
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By means of a spherical model of global postseismic deformation we perform an analysis of the postseismic stress diffusion process associated with the main seismic events which occurred in Chile and South Peru in the last century. Our aim... more
By means of a spherical model of global postseismic deformation we perform an analysis of the postseismic stress diffusion process associated with the main seismic events which occurred in Chile and South Peru in the last century. Our aim is to ascertain if the viscoelastic relaxation of the mantle and asthenosphere following the earthquakes, superimposed on the main mechanism of stress accumulation in the lithosphere, that is to say the subduction process, has, in some way, influenced the spatiotemporal pattern of seismic energy release in this region. Our investigations focus particularly on the areas where two important seismic gaps in an advanced mature state can be recognized. We found that the evolution of the postseismic stress might give a satisfactory explanation for the anomalous duration of the seismic quiescence in the gap areas and also for the possible filling of one of these gaps.
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Summary. — The postseismic response of a viscoelastic Earth can be computed analytically with a normal-mode approach, based on the application of propagator methods. This framework suffers from many limitations, mostly connected with the... more
Summary. — The postseismic response of a viscoelastic Earth can be computed analytically with a normal-mode approach, based on the application of propagator methods. This framework suffers from many limitations, mostly connected with the solution of the secular equation, whose degree scales with the number of viscoelas- tic layers so that only low-resolution models can be practically solved. Recently, a
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SUMMARY A comparison is performed between predictions of coseismic and post-seismic deformations, based on two diVerent earth models. The main purpose of this work is to clarify in a rigorous manner the role of sphericity in the... more
SUMMARY A comparison is performed between predictions of coseismic and post-seismic deformations, based on two diVerent earth models. The main purpose of this work is to clarify in a rigorous manner the role of sphericity in the assessment of both residual deformations and large-scale post-seismic motions. The two models considered in this study are commonly employed for predictions of post-seismic
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Research Interests: Viscoelasticity, Earth, Rheology, Stress, Stress field, and 18 moreSensitivity Analysis, Interpretation, Stratification, Multidisciplinary, Depth, Viscosity, Dislocation, Dislocations, CORE, Mantle, Model development, Time Dependent, Geophysical, Three Dimensional, Stress Transfer, Lithosphere, Earthquake Dynamics, and Seismic Hazard Assessment
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A comparison is performed between predictions of coseismic and post-seismic deformations, based on two different earth models. The main purpose of this work is to clarify in a rigorous manner the role of sphericity in the assessment of... more
A comparison is performed between predictions of coseismic and post-seismic deformations, based on two different earth models. The main purpose of this work is to clarify in a rigorous manner the role of sphericity in the assessment of both residual deformations and large-scale post-seismic motions. The two models considered in this study are commonly employed for predictions of post-seismic deformations.
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An Earth model subject to dislocations is studied in order to investigate the toroidal/poloidal content of global post-seismic deformation. Differently from previous analyses, our approach allows us to deal with some of the main... more
An Earth model subject to dislocations is studied in order to investigate the toroidal/poloidal content of global post-seismic deformation. Differently from previous analyses, our approach allows us to deal with some of the main complexities of the real Earth, such as sphericity, self-gravitation, and rheological stratification. The time-dependent ratio between toroidal and poloidal displacements is evaluated in the near and far-field of both strike and dip-slip lithospheric sources characterized by a finite length. Our findings show that post-seismic deformation changes its nature from poloidal to toroidal (and viceversa) on time-scales of several decades and over distances comparable with the dimensions of the lithospheric plates. The effects on horizontal velocities in North America of both poloidal and toroidal components induced by the Alaska 1964 earthquake is comparable with the signatures due to postglacial rebound; these two geodynamical phenomena are currently detectable by variations along baselines connecting Very Long Base Interferometry (VLBI) stations.
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... be sustained if the source region is viscoelastic; however, the transient response of the ... We use the technique developed here to investigate thoroughly the quasi-static surface deformations induced ... effects of a low-viscosity... more
... be sustained if the source region is viscoelastic; however, the transient response of the ... We use the technique developed here to investigate thoroughly the quasi-static surface deformations induced ... effects of a low-viscosity asthenosphere on the rates of deformation detected at ...
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... Claudio Gariazzo a , Corresponding Author Contact Information , E-mail The Corresponding Author , Camillo Silibello b , Sandro Finardi b , Paola Radice b , Antonio Piersanti b , Giuseppe Calori b , Angelo Cecinato c , Cinzia Perrino c... more
... Claudio Gariazzo a , Corresponding Author Contact Information , E-mail The Corresponding Author , Camillo Silibello b , Sandro Finardi b , Paola Radice b , Antonio Piersanti b , Giuseppe Calori b , Angelo Cecinato c , Cinzia Perrino c , Fabio Nussio d , Marco Cagnoli d ...
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SUMMARY The deformation at the core–mantle boundary produced by the 2004 Sumatra earthquake is investigated by means of a semi-analytic theoretical model of global coseismic and postseismic deformation, predicting a millimetric coseismic... more
SUMMARY The deformation at the core–mantle boundary produced by the 2004 Sumatra earthquake is investigated by means of a semi-analytic theoretical model of global coseismic and postseismic deformation, predicting a millimetric coseismic perturbation over a large portion of the core–mantle boundary. Spectral features of such deformations are analysed and discussed. The time-dependent postseismic evolution of the elliptical part of the gravity field (J 2) is also computed for different asthenosphere viscosity models. Our ...