Earth-printshttps://www.earth-prints.orgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Tue, 27 Oct 2020 04:12:44 GMT2020-10-27T04:12:44Z5041Seismic noise at Solfatara Volcano (Campi Flegrei, Italy): acquisition techniques and first resultshttp://hdl.handle.net/2122/3562Title: Seismic noise at Solfatara Volcano (Campi Flegrei, Italy): acquisition techniques and first results
Authors: Petrosino, S.; Damiano, N.; Cusano, P.; Veneruso, M.; Zaccarelli, L.; Torello, V.; Del Pezzo, E.
Abstract: In the period 2-6 April 2007 a seismic survey
was carried out at Solfatara Volcano, with the
aim of inferring the shallow structure and evaluating
local site effects. Seismic noise was recorded
by five circular seismic arrays deployed in different
areas of the crater. The geometry was
designed in order to obtain also a sub-configuration
consisting of two profiles oriented in the NS
and E-W directions. An other seismic station
was installed on the eastern rim of the crater, for
a hardrock reference. A preliminary spectral
analysis was performed on some samples of seismic
noise recorded during the experiment.
As future development, surface wave dispersion
will be obtained by using array techniques,
such as the Spatial Autocorrelation
method (SPAC) of Aki (1957) and its recent modifications
(MSPAC, Bettig et al, 2001; CCA, Cho
et al., 2004). The shear-wave velocity models
will be inferred for each array from the inversion
of the dispersion curves. Moreover experimental
site transfer functions will be evaluated for each
station, using both Nakamura’s technique and the
reference-site spectral ratio method.
The high density of the deployment and
the large number of the sampled sites will allow
to obtain a detailed shallow velocity structure
and to map resonance frequencies and amplification
values in different areas of the crater.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/2122/35622008-01-01T00:00:00ZOn the uncertainties of seismic parameters: a Bayesian framework for their estimation using Brune's modelhttp://hdl.handle.net/2122/8428Title: On the uncertainties of seismic parameters: a Bayesian framework for their estimation using Brune's model
Authors: Caciagli, Marco; Garcia-Aristizabal, Alexander; Selva, Jacopo
Abstract: The estimation of seismic parameters from ground-motion records is subject to many uncertainties, such as:
(i) parameterization, modeling procedures and underlying hypotheses, (ii) approximated input parameters, (iii) instrumental errors on records and their impact in data post-processing, (iv) procedures to estimate model’s parameters. However these uncertainties are rarely treated and propagated to the final results.
For example, on one side, density of rocks, velocity model, geometrical spreading, radiation pattern are just some of the common parameters needed to estimate the main seismic parameters of an earthquake and are generally used as average values. On the other side, uncertainties derived from the acquisition system and processing of the data are often neglected. Nevertheless, in many cases these uncertainties may be particularly important, as for example in the analysis of historical
earthquakes, where both instrumental response and treatment of analog records intrinsically imply non negligible sources of uncertainty.
Here, we present a new Bayesian procedure to estimate seismic parameters that allows: (i) to obtain a robust estimation of the Brune’s model parameters (Brune 1970, 1971) and relatives uncertainties, (ii) to account for the uncertainty related to the Earth model, and (iii) to propagate such uncertainties on the estimation of seismological parameters (seismic moment, moment magnitude, radius of the circular source zone and static stress drop). It is important to highlight that this study does not want to discuss the validity or the physical significance of the Brune’s model, but it is focused on the details of how to fit it on a dataset in order to evaluate the seismological parameters, accounting and properly propagating a rather large range of uncertainties. These capabilities of the proposed procedure are finally demonstrated through an illustrative application analyzing seismic records from historical events.
Mon, 03 Dec 2012 00:00:00 GMThttp://hdl.handle.net/2122/84282012-12-03T00:00:00ZIntegration of stochastic models for long-term eruption forecasting into a Bayesian event tree scheme: a basis method to estimate the probability of volcanic unresthttp://hdl.handle.net/2122/8572Title: Integration of stochastic models for long-term eruption forecasting into a Bayesian event tree scheme: a basis method to estimate the probability of volcanic unrest
Authors: Garcia-Aristizabal, A.; Selva, J.; Fujita, E.
Abstract: Eruption forecasting refers, in general, to the
assessment of the occurrence probability of a given erup-
tive event, whereas volcanic hazards are normally associated
with the analysis of superficial and evident phenomena
that usually accompany eruptions (e.g., lava, pyroclastic
flows, tephra fall, lahars, etc.). Nevertheless, several hazards
of volcanic origin may occur in noneruptive phases dur-
ing unrest episodes. Among others, remarkable examples
are gas emissions, phreatic explosions, ground deforma-
tion, and seismic swarms. Many of such events may lead to
significant damages, and for this reason, the “risk” associ-
ated to unrest episodes could not be negligible with respect
to eruption-related phenomena. Our main objective in this
paper is to provide a quantitative framework to calculate
probabilities of volcanic unrest. The mathematical frame-
work proposed is based on the integration of stochastic mod-
els based on the analysis of eruption occurrence catalogs
into a Bayesian event tree scheme for eruption forecast-
ing and volcanic hazard assessment. Indeed, such models
are based on long-term eruption catalogs and in many
cases allow a more consistent analysis of long-term tem-
poral modulations of volcanic activity. The main result of
this approach is twofold: first, it allows to make inferences
about the probability of volcanic unrest; second, it allows
to project the results of stochastic modeling of the eruptive
history of a volcano toward the probabilistic assessment of
volcanic hazards. To illustrate the performance of the pro-
posed approach, we apply it to determine probabilities of
unrest at Miyakejima volcano, Japan.
Tue, 12 Feb 2013 00:00:00 GMThttp://hdl.handle.net/2122/85722013-02-12T00:00:00ZPatterns in Climate-Related Parameters as Proxy for Rainfall Deficiency and Aridity: Application to Burkina Fasohttp://hdl.handle.net/2122/13683Title: Patterns in Climate-Related Parameters as Proxy for Rainfall Deficiency and Aridity: Application to Burkina Faso
Authors: Garcia, Alexander; Bucchignani, Edoardo; Manzi, Maria Paola
Abstract: This work is aimed to propose a methodology for the identification of areas for which extreme climatological conditions may intensify aridity processes and rainfall deficiency. The proposed procedure, which is based on the analysis of climate projections derived from high-resolution regional simulations, is composed of three main elements. First, extreme temperature, extreme precipitation, and extreme dry periods (in terms of consecutive dry days) are modeled using extreme value theory. Second, an aridity index is used as a proxy of long-term
processes leading to aridity. Third, clustering techniques are used to group zones with similar climatic parameters. In this way, areas with the more extreme climate conditions are identified. Possible effects due to selected climate-change scenarios are considered by analyzing possible nonstationary conditions in extreme events and by performing calculations in both a historical period and a projection period (where different
scenarios are considered). An application of the proposed procedure is implemented in an area around Ouagadougou, Burkina Faso. From the analyses, it emerged that the eastern part of the case study area will experience both large rainfall deficit and the highest extreme temperatures. Those two aspects, combined with a potential water demand increase (due to the increasing of number of inhabitants), may favor the
intensification of the aridity processes.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/2122/136832017-01-01T00:00:00Z