Papers by Francesco Mulargia
Geophysical Journal International, Jun 1, 1978
Calculations of the thermodynamical Gruneisen's gamma as a function of temperature and volume for... more Calculations of the thermodynamical Gruneisen's gamma as a function of temperature and volume for iron are presented. The ranges of the relevant pressures and temperatures extend to those corresponding to the Earth's core. The various crystal structures of iron and several kinds of intermolecular potential functions are considered. It is found that it is not possible to describe the Gruneisen's gamma for iron with the accuracy needed for an assessment of the thermal state of the core mainly because the available experimental data do not allow a definite choice among the possible potential functions.
Earthquake Science and Seismic Risk Reduction, 2003
ABSTRACT
Earthquake Science and Seismic Risk Reduction, 2003
ABSTRACT
Bulletin of the Seismological Society of America, Aug 1, 1989
The clustering properties of Italian seismicity are analyzed statistically on the basis of the Is... more The clustering properties of Italian seismicity are analyzed statistically on the basis of the Istituto Nazionale di Geofisica seismic catalog, The traditional generalized Poisson model is found to be inefficient for a quantitative analysis. Based on the influence region, a new model is developed that allows to assess some spatial features of clustering as well. The results are the following: (1) there is no evidence of migration; (2) clustering is mostly originated by main shock-aftershock sequences; (3) cluster parameters are function of the region studied; (4) several different parameterizations are possible; and (5) the best fit is provided by an influence region of respectively 14 days to 60 days and 80 to 140 km.
arXiv: Astrophysics of Galaxies, 2017
A number of earth's tremor spectral peaks show a persistent narrow bandwidth incompatible wit... more A number of earth's tremor spectral peaks show a persistent narrow bandwidth incompatible with any geophysical or instrumental origin. These peaks, located at frequencies lower than a few mHz, are in principle consistent with the earth strain waves induced by monochromatic gravitational waves. Exploring this hypothesis under the current cosmological constraints yields that the tremor peaks below 2 mHz are in apparently significant coincidence with the theoretical emission of two binary systems each consisting of a small main sequence star with mass $\sim 10^{-1} M_{\odot}$, captured by Sgr A* in a close orbit.
Geophysical Journal International, 2018
Independent multi-year analyses of Earth tremor have suggested a continuous excitation of Earth n... more Independent multi-year analyses of Earth tremor have suggested a continuous excitation of Earth normal modes by ocean storms, but also a number of unexplained spectral peaks extraneous to them, mostly in the 0.2-2 mHz frequency band. We reassess the worldwide existence of such peaks by stacking the multitaper high-resolution spectra of all stations of the International Geodynamics and Earth Tide Service superconducting gravimeter network with at least 30 months of uninterrupted record, analysing a global epoch of 656 months. The analysis, beyond showing the predominance of 0 S n , n = 0, .., 12 Earth spheroidal modes, confirms the existence of unexplained spectral peaks which (1) cannot be ascribed to instrumental noise, (2) occur at frequencies extraneous to Earth normal modes, (3) have a statistical significance comparable to them and (4) appear incompatible with any natural or anthropic terrestrial source. While at odds with the hypothetical Earth 'tune in' on a continuum detectable gravitational wavefield, the peaks appear to be compatible in terms of amplitude, frequency and-according to cosmological constraints-expected number, with the independently calculated gravitational wave monochromatic emission of a few binary systems consisting of a star with mass ∼1/10 of the sun captured in close orbit by the supermassive black hole at the centre of our galaxy.
Physics of the Earth and Planetary Interiors, 2017
Even though it has never been validated by objective testing, Probabilistic Seismic Hazard Analys... more Even though it has never been validated by objective testing, Probabilistic Seismic Hazard Analysis (PSHA) has been widely used for almost 50 years by governments and industry in applications with lives and property hanging in the balance, such as deciding safety criteria for nuclear power plants, making official national hazard maps, developing building code requirements, and determining earthquake insurance rates. PSHA rests on assumptions now known to conflict with earthquake physics; many damaging earthquakes, including the 1988 Spitak, Armenia, event and the 2011 Tohoku, Japan, event have occurred in regions relatively rated low-risk by PSHA hazard maps. No extant method, including PSHA, produces reliable estimates of seismic hazard. Earthquake hazard mitigation should be recognized to be inherently political, involving a tradeoff between uncertain costs and uncertain risks. Earthquake scientists, engineers, and risk managers can make important contributions to the hard problem of allocating limited resources wisely, but government officials and stakeholders must take responsibility for the risks of accidents due to natural events that exceed the adopted safety criteria.
Monthly Notices of the Royal Astronomical Society: Letters, 2016
Even in absence of earthquakes, each site on earth experiences continuous elastic vibrations whic... more Even in absence of earthquakes, each site on earth experiences continuous elastic vibrations which are mostly traced to the non-linear interactions of sea waves. However, the fine structure of the spectrum at mHz frequencies shows hundreds of highly significant narrow bandwidth peaks, with a persistence and a coincidence with solar acoustic eigenmodes which are incompatible with any geophysical origin. The feasibility of a common cosmic origin is evaluated through an estimate of the gravitational wave cross-section of the earth, combined with its elastic response and with the stochastic amplification produced by the interference of the cosmic signal with tremor of oceanic origin. The measured spectral peaks appear compatible with a gravitational monochromatic illumination at strains h 10 −20. We analize in detail the band around 2.614 mHz, where the binary white dwarf J0651+2844-which is the second strongest known gravitational stellar source-is expected to emit. Compatible spectral tremor peaks are found for both the earth and the sun, but their amplitude is 3 o.m. larger than independent estimates, so that a gravitational source attribution would call for a variety of unknown non-luminous sources with definite mass-distance ratios.
Tectonophysics, 1990
We estimate the viscosity in the Earth's mantle through a material science approach. Since refine... more We estimate the viscosity in the Earth's mantle through a material science approach. Since refined theoretical formulations are still difficult to apply without drastic approximations due to the very scarce knowledge of the material properties of the mantle, we rely on a semi-empirical approach. The most effective semi-empirical formulation accounts for the effect of temperature and pressure on creep utilizing the melting temperature as a scaling parameter. There is no well established method of estimating the effect of polymorphic phase transitions (which in any case are not definitely known in the mantle) and only very rough estimates are possible. Inaccuracies of a few orders of magnitude must be allowed. We apply it to the mantle and analyze the stability of the results against the feasible range of rheology types, geothermal profile/melting curves, presence of boundary layers and related temperature jump, and material constants. In spite of a large uncertainty in the results, a comparison with the available studies on global Earth rheology (with the proviso that the two sets are not always compatible) based on post-glacial rebound, geoid anomalies and post-seismic deformation allows to derive the combination rules for the different variables and to depict the possible scenarios for the thermodynamic state and the rheology of the mantle. For example, Newtonian rheology is compatible only with some particular geothermal profiles and with some given sets of material parameters.
Tectonophysics, 1987
The scope of the present work is to identify the Italian seismic regions, toward a better definit... more The scope of the present work is to identify the Italian seismic regions, toward a better definition of the active tectonic structures. Spatial filtering is used, together with the recently released PFG-ENEL seismic catalog which covers the period 1000-1980. Any such approach based on catalog data has to acknowledge that catalog reliability and resolving power are functions of time and position. These problems, which can potentially lead to an incorrect regionalization, can be attributed to catalog incompleteness. The effects of the latter are estimated and correlated through a new approach, which deterrnines the completeness interval from the pIot of the cumulative number of events versus time, and measures the degree of incompleteness by assuming it to be a function with a continuous first derivati ve. In this way, ali the information present in the catalog can be used in contour mapping by an appropriate weighting of incomplete parts in spatiaI filtering. On the other hand, the choice of the weight factors involves some arbitrary judgement and therefore introduces a bias. In order to reach an objective result, different weighting schemes covering ali feasible choices are tried, and the final regionalization is concluded to be valid only if it is stable. A fair stability is obtained and it is henceforth possible to conclude that the seismic regions identified represent an unbiased picture of the real situation. Interestingly, different areas exhibit a different seismic character, some being capable of frequent activity but never exceeding moderate magnitude values, and others being characterized by a scarcity of moderate events combined with the capability of occasionaI large earthquakes. Italian seismic catalog provides a large database of over 37,000 events relating to the period 1000-1980 A.D. AlI events, except the ones in this
Tectonophysics, 1991
Abstract Southeastern Sicily, which has frequently experienced ruinous earthquakes in historic ti... more Abstract Southeastern Sicily, which has frequently experienced ruinous earthquakes in historic times, has only been site of minor activity in the last two centuries. Two precision levelling surveys that we carried out in 1983 and 1989 detected high rates of crustal ...
Rock Mechanics and Rock Engineering, 2004
Static and dynamic elastic moduli of Calcare Massiccio (mudstone-limestone) have been measured as... more Static and dynamic elastic moduli of Calcare Massiccio (mudstone-limestone) have been measured as a function of frequency over nine decades, using three different standard methods: uniaxial 'static' compression, dual cantilever forced oscillations, and measurement of ultrasonic velocities. An accurate critical comparison using the same techniques on a poly-methyl-methacrylate (PMMA) material shows that an unresolvable 10 to 20% bias exists in the two 'low' frequency standard techniques, whereas the ultrasonic measurements are more accurate and reproducible within 5%. No significant frequency dependence is found for Calcare Massiccio, which gives a Young's modulus of (75 AE 7) GPa and a Poisson's ratio of (0.28 AE 0.02).
Pure and Applied Geophysics PAGEOPH, 1985
The apparent magnitude of an earthquake y is defined as the observed magnitude value and differs ... more The apparent magnitude of an earthquake y is defined as the observed magnitude value and differs from the true magnitude m because of the experimental noise n. If f (m) is the density distribution of the magnitude m, and if g(n) is the density distribution of the error n, then the density distribution of y is simply computed by convolvingfand g, i.e. h(y) =f*o. If the distinction between y and m is not realized, any statistical analysis based on the frequencymagnitude relation of the earthquake is bound to produce questionable results. In this paper we investigate the impact of the apparent magnitude idea on the statistical methods that study the earthquake distribution by taking into account only the largest (or extremal) earthquakes. We use two approaches: the Gumbel method based on Gumbel theory (GUMBEL, 1958), and the Poisson method introduced by EPSTEIN and LOMNITZ (1966). Both methods are concerned with the asymptotic properties of the magnitude distributions. Therefore, we study and compare the asymptotic behaviour of the distributions h (y) andf(m) under suitable hypotheses on the nature of the experimental noise. We investigate in detail two dinstinct cases: first, the two-side limited symmetrical noise, i.e. the noise that is bound to assume values inside a limited region, and second, the normal noise, i.e. the noise that is distributed according to a normal symmetric distribution. We further show that disregarding the noise generally leads to biased results and that, in the framework of the apparent magnitude, the Poisson approach preserves its usefulness, while the Gumbel method gives rise to a curious paradox.
Pure and Applied Geophysics PAGEOPH, 1987
... STEFANO TINTI, ~ ROSSELLA RIMONDI ~ and FRANCESCO MULARGIA ... laws have been suggested, most... more ... STEFANO TINTI, ~ ROSSELLA RIMONDI ~ and FRANCESCO MULARGIA ... laws have been suggested, mostly based on purely experimental grounds, that differ from the GUTENBERg-RICHTER (GR) model, especially at the highest magnitudes (see eg, COSENTINO and LuzIo ...
Physics of the Earth and Planetary Interiors, 1989
... Publishers BV, Amsterdam Printed in The Netherlands The GrUneisen parameter and adiabatic gra... more ... Publishers BV, Amsterdam Printed in The Netherlands The GrUneisen parameter and adiabatic gradient in the Earths interior 221 Francesca Quareni 1st it uto Nazionale di Geofisica, 40127 Bologna (Italy) Francesco Mulargia Dipartimento di ... 29, SW Hiki and Granato (1966). ...
Physics of the Earth and Planetary Interiors, 1990
... The main scales are those of Heirt zier et al ... Let us consider two variables x and y. Firs... more ... The main scales are those of Heirt zier et al ... Let us consider two variables x and y. First, the values of the two variables are ranked; all the possible pairs of x elements (xe, x1 fi) and the corresponding pairs (ye, y) are then considered; we define V= (x1x)(y,y3) The Kendall score S ...
Journal of Volcanology and Geothermal Research, 1985
Lava flows produced during Etna flank eruptions represent severe hazards for the nearby inhabited... more Lava flows produced during Etna flank eruptions represent severe hazards for the nearby inhabited areas, which can be protected by adopting prompt mitigation actions, such as the building of diversion barriers. Lava diversion measures were attempted recently during the 1983, 1991-93, 2001 and 2002 Etna eruptions, although with different degrees of success. In addition to the complexity of barrier construction (due to the adverse physical conditions), the time available to successfully slow the advance of a lava flow depends on the lava effusion rate, which is not easily measurable. One method to estimate the average lava effusion rate over a specified period of time is based on a volumetric approach; i.e. the measurement of the volume changes of the lava flow over that period. Here, this has been compared to an approach based on thermal image processing, as applied to estimate the average effusion rates of lava flows during the 1981 and 2001 Etna eruptions. The final volumes were measured by the comparison of pre-eruption and post-eruption photogrammetric digital elevation models and orthophotographs. Lava volume growth during these eruptions was estimated by locating the flow-front positions from analyses of scientific papers and newspapers reports, as well as from helicopter photographs. The analyses of these two eruptions contribute to the understanding of the different eruptive mechanisms, highlighting the role of the peak effusion rate, which represents a critical parameter for planning of mitigation actions and for hazard evaluation.
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Papers by Francesco Mulargia