New Insights into Long-Term Aseismic Deformation and Regional Strain Rates from GNSS Data Inversion: The Case of the Pollino and Castrovillari Faults

We present a novel inverse method for discriminating regional deformation and long-term fault creep by inversion of GNSS velocities observed at the spatial scale of intraplate faults by exploiting the different spatial signatures of these two mechanisms. In doing so our method provides a refined estimate of the upper bound of the strain accumulation process. […]

On Earthquake Detectability by the Next-Generation Gravity Mission

Earthquakes have been studied by means of seismometers recording the elastic waves travelling through the interior of our planet. Global Navigation Satellite System and Synthetic Aperture Radar surveys, measuring surface displacements, have provided additional information on earthquakes, as well as on those solid Earth processes responsible for them, such as subduction, collision and extension and […]

Joint estimate of the coseismic 2011 Tohoku earthquake fault slip and postseismic viscoelastic relaxation by GRACE data inversion

Satellite-derived gravity data offer a novel perspective for understanding the physics of megathrust earthquakes at subduction zones. Nonetheless, their temporal resolution and observational errors make it difficult to discern the different phases of the seismic cycle, as the elastostatic deformation (coseismic) and the stress relaxation by viscous flow (post-seismic). To overcome these difficulties and to […]

The physics of earthquakes from space gravity missions

Developments in the physical modelling of the Earth’s interior and space geodesy make it possible nowadays to exploit the gravity signature and deformation patterns, including their time variations, caused by megathrust earthquakes at subduction zones with moment magnitude Mw higher than 9.0, as the 2004 Sumatran and 2011 Tohoku-Oki ones. In order to achieve these goals, it […]

Time dependent geoid anomalies at subduction zones due to the seismic cycle

We model the geoid anomalies excited during a megathrust earthquake cycle at subduction zones, including the interseismic phase and the contribution from the infinite series of previous earthquakes, within the frame of self-gravitating, spherically symmetric, compressible, viscoelastic Earth models. The fault cuts the whole 50 km lithosphere, dips 20°, and the slip amplitude, together with […]

Co-seismic slip distribution of the 2011 Tohoku (Mw 9.0) earthquake inverted from GPS and space-borne gravimetric data

Data obtained by GRACE (Gravity Recovery and Climate Experiment) have been used to invert for the seismic source parameters of megathrust earthquakes under the assumption of either uniform slip over an entire fault or a point-like seismic source. Herein, we further extend the inversion of GRACE long-wavelength gravity changes to heterogeneous slip distributions during the […]

Joint estimate of the rupture area and slip distribution of the 2009 L’Aquila earthquake by a Bayesian inversion of GPS data

Usually, when inverting geodetic data to estimate the slip distributions on a fault, the area is made large enough to more than cover the rupture zone, with regularization producing regions of large slip with very small slip over the rest of the surface. We have developed a new inverse method which assumes that nonzero slip […]

Global Dynamics of the Earth: Applications of Viscoelastic Relaxation Theory to Solid-Earth and Planetary Geophysics

This volume opens up new perspectives on the physics of the Earth’s interior and planetary bodies for graduate students and researchers working in the fields of geophysics, planetary sciences and geodesy. It looks at our planet in an integrated fashion, linking the physics of its interior to geophysical and geodetic techniques that record, over a […]

Residual polar motion caused by coseismic and interseismic deformations from 1900 to present

We challenge the perspective that seismicity could contribute to polar motion by arguing quantitatively that, in first approximation and on the average, interseismic deformations can compensate for it. This point is important because what we must simulate and observe in Earth Orientation Parameter time-series over intermediate timescales of decades or centuries is the residual polar […]

On the seismic perturbation due to a fault system: its evaluation beyond the epicentral reference frame

Previous formalisms for determining the static perturbation of spherically symmetric self- gravitating elastic Earth models due to displacement dislocations deal with each infinitesimal element of the fault system in its epicentral reference frame. In this work, we overcome this restriction and present novel and compact formulas for obtaining the perturbation due to the whole fault […]

The 2011 Tohoku (MW = 9.1) co-seismic slip pattern shaped by smoothing criteria and GPS, OB-GPS data

In the literature, the inverted coseismic slip models from seismological and geodetic data for the 2011 Tohoku-Oki earthquake portray significant discrepancies, in particular regarding the intensity and the distribution of the rupture near the trench. For a megathrust earthquake, it is difficult to discern the slip along the shallow part of the fault from the […]

Power-law Maxwell rheologies and the interaction between tectonic and seismic deformations

In a lithosphere where dislocation creep dominates the steady-state flow and the viscosity is stress-dependent, the equilibrium between tectonic stress and strain rate is broken after an earthquake due to the sudden coseismic stress change. The imbalance between tectonic stress and strain rate manifests itself during the post-seismic phase and, when seismic stress is comparable […]

Gravitational seismology retrieving Centroid-Moment-Tensor solution of the 2011 Tohoku earthquake

Mass rearrangement within the crust and lithospheric mantle and ocean water redistribution caused by great earthquakes are made visible by their coseismic gravity signature, nowadays detectable by the Gravity Recovery And Climate Experiment (GRACE) space mission. Here we present a novel procedure for estimating the principal seismic source parameters (hypocenter and moment tensor) that relies […]

Compressible viscoelastodynamics of a spherical body at long time scales and its isostatic equilibrium

The problem of compressibility in modelling of viscoelastic deformations of planetary bodies is still a topic under discussion. Studies facing this topic discuss the error when considering a stratification of layers with constant material parameters. But homogeneous compressible layers imply that the initial state is not stable. So, any perturbation method applied to this type […]

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

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

A finite fault model of the great 2011 Tohoku earthquake (Mw = 9.1) from inversion of GRACE gravity data

The co-seismic slip distribution of the 2011 Tohoku megathrust earthquake is constrained from GeoForschungsZentrum (GFZ) Gravity Recovery and Climate Experiment (GRACE) Level 2 data time series and our self-gravitating, compressible 1-D Earth model. After spatial localization of space gravity data in the surrounding of the U.S. Geological Survey (USGS) epicenter by means of orthogonal Slepian […]

The compressional and compositional stratifications in Maxwell earth models: the gravitational overturning and the long-period tangential flux

We analyse self-gravitating compressible Maxwell earth models with compressional and com- positional stratifications by taking into account the continuous variations of the initial density and of the bulk modulus. We derive the analytical solution in the Laplace domain of an earth model composed of a homogeneous inviscid core and a viscoelastic mantle characterized by a […]

A comparative analysis of the solutions for a Maxwell Earth: the role of the advection and the buoyancy force

Within the normal mode relaxation theory, we thoroughly analyze and compare the exact compressible and incompressible solution for a viscoelastic stratified Earth model with an approximated analytical one, where the ratio between gravity and radial distance from the Earth’s centre is considered constant in each layer of the model. We implement an algorithm, based on […]