A. Antonioli

Spherical versus flat models of coseismic and postseismic deformations

We perform an exhaustive study of coseismic and postseismic surface deformations induced by shear dislocations using flat and spherical Earth models. Our aim is to examine the effects of the spherical geometry, the vertical layering, and the self-gravitation on surface displacement field. For a 100 km long fault, spherical and flat models produce comparable coseismic deformations up to a distance of ∼300 km from the epicenter. This distance is sensibly reduced in the postseismic regime and when infinitely long strike-slip faults are considered. The differences between predictions based on flat and spherical models are due both to their global geometry and the effect of the gravity forces. Self-gravitation has a minor role with respect to that of sphericity for surface coseismic deformations, while in the postseismic regime its effects increase considerably. As a case study, we consider the coseismic and postseismic deformations due to the great 1960 Chilean earthquake. The results of the spherical stratified model differ sensibly from those of a flat uniform model. Moreover, within the framework of spherical Earth models, the rheological stratification plays a major role in determining the pattern of the displacement field. We show that the present-day rates of vertical and horizontal deformations are considerably large (∼10 -2 m yr -1 ) for an asthenospheric viscosity ranging from 10 19 to 10 20 Pa s. These rates, which could possibly be detected by geodetic investigations, are found to be also sensitive to the rheological properties of the mantle beneath the asthenosphere.

Modeling Earth's post‐glacial rebound

Efforts to mathematically model the Earths post-glacial rebound, or, in general, long-term planetary-scale viscoelastic deformations, have been ongoing for several decades. Unfortunately, research in the post-glacial rebound community has not been characterized by much exchange of knowledge. Groups around the world have developed their code independently, sometimes with profoundly different approaches, occasionally leading to inconsistent results [e.g., Boschi et al., 1999]. Postglacial Rebound Calculator (TABOO) is a post-glacial rebound software that is being made freely available (through Samizdat Press at http://samizdat.mines.edu/taboo/) in the hope that it might become a common reference for all post-glacial rebound researchers. TABOO is portable and has been tested on Unix, Linux, and Windows systems; all it requires is a Fortran90 compiler supporting quadruple precision. The software is easy to use. It comes with a detailed guide that can work as a quick reference cookbook, and it is also accompanied by a textbook, The Theory Behind TABOO, collecting the most significant theoretical results from post-glacial rebound literature. TABOO is not a “black-box,” although it may easily be used as such. The entire source code is provided and should be easy to understand for intermediate-level Fortran programmers.

Near-field propagation of tsunamis from megathrust earthquakes

We investigate controls on tsunami generation and propagation in the near-field of great megathrust earthquakes using a series of numerical simulations of subduction and tsunamigenesis on the Sumatran forearc. The Sunda megathrust here is advanced in its seismic cycle and may be ready for another great earthquake. We calculate the seafloor displacements and tsunami wave heights for about 100 complex earthquake ruptures whose synthesis was informed by reference to geodetic and stress accumulation studies. Remarkably, results show that, for any near-field location: (1) the timing of tsunami inundation is independent of slip-distribution on the earthquake or even of its magnitude, and (2) the maximum wave height is directly proportional to the vertical coseismic displacement experienced at that location. Both observations are explained by the dominance of long wavelength crustal flexure in near-field tsunamigenesis. The results show, for the first time, that a single estimate of vertical coseismic displacement might provide a reliable short-term forecast of the maximum height of tsunami waves.

Mazara del Vallo Tide Gauge Observations (1906–16): Land Subsidence or Sea-Level Rise?

ABSTRACT Olivieri, M.; Spada, G.; Antonioli, A., and Galassi, G., 2015. Mazara del Vallo tide gauge observations (1906–16): Land subsidence or sea-level rise? Tide gauge (TG) data constitute an invaluable tool for the interpretation of short- and long-term sea-level changes occurring in the Mediterranean Sea. The complex geophysical environment and the limited amount of sufficiently long records make the interpretation of local signals problematic because these are often affected by interlacing processes. Starting from newly disclosed TG records from the site of Mazara del Vallo (SW Sicily), we analyze simultaneously the time series available from other locations in Sicily across the beginning of the 20th century (Messina and Palermo). Despite the limited record length, we show that these observations provide new perspectives on the causes of the observed sea-level variations in the central Mediterranean region, and, in particular, they challenge previous tenets regarding the extent of land movements caused by the 1908 Messina Straits earthquake.

Results from INSAR monitoring of the 2010–2011 New Zealand seismic sequence: EA detection and earthquake triggering

We used a variety of SAR-based techniques to measure the crustal deformation associated to the Darfield and Christchurch earthquakes, New Zealand. We detected clear post-seismic signals of the Darfield earthquake, and a pre-seismic signal spatially and temporally associated to the Christchurch earthquake. The small pre-seismic signal (~25 mm) has an opposite polarity of the much larger co-seismic one (~150 mm) in the same area.