Bulletin of the Seismological Society of America, 2014
On April 6 2009, a Mw 6.3 earthquake shook Central Italy and caused heavy damage and deaths in th... more On April 6 2009, a Mw 6.3 earthquake shook Central Italy and caused heavy damage and deaths in the city of L'Aquila. The region is characterized by strong geological heterogeneities and prominent topographic features, leading to remarkable site effects. We present a comparison of the seismograms recorded by the Italian National Seismic Network and by the Italian National Accelerometric Network and synthetic seismograms calculated based upon a spectral-element method (SEM). The SEM simulations take into account a kinematic seismic source obtained from a 1D geodetic and seismological inversion, the main structural discontinuities, high-resolution topography, and state-of-art of local/regional traveltime tomography. The approach will lead to a full 3D waveform seismic source inversion, and will ultimately form the basis of full waveform tomography of the Abruzzi region.
Abstract The devastating megathrust earthquake of December 26 2004 off the west coast of northern... more Abstract The devastating megathrust earthquake of December 26 2004 off the west coast of northern Sumatra has been probably the largest since the 1960 Chile event. The occurrence of this event revived the debate, among the scientific community, upon several open geophysical problems possibly connected with the energy release of giant earthquakes. One of these problems concerns the origin of geomagnetic jerks and its eventual relationship with large seismic activity. Though a final answer to this question seems not to ...
We perform an extensive analysis of the low-degree gravity field harmonics measured by the GRACE ... 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.
A spherically symmetric Earth model with viscoelastic rheology is used to study the postseismic r... 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
One of the most recent novelties in volcanology is the finding of a statistically significant inf... 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
... Abstract. Estimating Lateral Structure in the Earth’s Outer Core. Estimating Lateral Structur... more ... Abstract. Estimating Lateral Structure in the Earth’s Outer Core. Estimating Lateral Structure in the Earth’s Outer Core. Antonio Piersanti. ...
By means of a spherical Earth model with Maxwell rheology, an analysis of the postseismic deforma... 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.
Large earthquakes are a potentially important source of relative sea level variations, since they... 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
Bulletin of the Seismological Society of America, 2014
On April 6 2009, a Mw 6.3 earthquake shook Central Italy and caused heavy damage and deaths in th... more On April 6 2009, a Mw 6.3 earthquake shook Central Italy and caused heavy damage and deaths in the city of L'Aquila. The region is characterized by strong geological heterogeneities and prominent topographic features, leading to remarkable site effects. We present a comparison of the seismograms recorded by the Italian National Seismic Network and by the Italian National Accelerometric Network and synthetic seismograms calculated based upon a spectral-element method (SEM). The SEM simulations take into account a kinematic seismic source obtained from a 1D geodetic and seismological inversion, the main structural discontinuities, high-resolution topography, and state-of-art of local/regional traveltime tomography. The approach will lead to a full 3D waveform seismic source inversion, and will ultimately form the basis of full waveform tomography of the Abruzzi region.
Abstract The devastating megathrust earthquake of December 26 2004 off the west coast of northern... more Abstract The devastating megathrust earthquake of December 26 2004 off the west coast of northern Sumatra has been probably the largest since the 1960 Chile event. The occurrence of this event revived the debate, among the scientific community, upon several open geophysical problems possibly connected with the energy release of giant earthquakes. One of these problems concerns the origin of geomagnetic jerks and its eventual relationship with large seismic activity. Though a final answer to this question seems not to ...
We perform an extensive analysis of the low-degree gravity field harmonics measured by the GRACE ... 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.
A spherically symmetric Earth model with viscoelastic rheology is used to study the postseismic r... 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
One of the most recent novelties in volcanology is the finding of a statistically significant inf... 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
... Abstract. Estimating Lateral Structure in the Earth’s Outer Core. Estimating Lateral Structur... more ... Abstract. Estimating Lateral Structure in the Earth’s Outer Core. Estimating Lateral Structure in the Earth’s Outer Core. Antonio Piersanti. ...
By means of a spherical Earth model with Maxwell rheology, an analysis of the postseismic deforma... 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.
Large earthquakes are a potentially important source of relative sea level variations, since they... 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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Papers by Antonio Piersanti