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Strong motion inversion for slip distribution on a finite fault using strong motion data: L’Aquila 2009 earthquake
No full textIdentification of Possible Velocity Pulses in Earthquake Near Fault Regions by Using Machine Learning
Full text linkPulse shape ground motions have been identified as imposing extreme demands on structures and they are of interest in the fields of seismology and earthquake engineering. Algorithms are established to distinguish pulse shape signals from ordinary earthquake signal such as Mavroeidis & Papageorgiou, 2003 and Baker, 2007. Baker's algorithm can detect possible pulses and their periods in given waveform by using more convenient methods. We used various parameters such as PGA, PGV, epicentral distance, Mw along with others and combined them with Baker's algorithm to construct the database. Our database contain near fault waveform of significant crustal earthquakes in hazardous seismic zones. The parameters that we choose to use are easy to determine not only from real earthquake data but also from seismic hazard maps. TensorFlow and Scikit-learn are used in order to process the parameters and establish a reliable algorithm. Both numeric values which are related with earthquake and station position and whole waveform, as numeric and image sense, are used in machine learning. Different algorithms are compared with each other in order to establish a convenient method to understand the possibility of occurrence of pulse shape signals on near fault regions
Seismicity of Eastern Alps and North western Dinaric Alps
Full text linkOur study region is placed on Adriatic Plate and the boundaries are Dinaric Orogenic Belt, Carnic, Tolmezzo and Julian Alps. The area has normal, reverse and strike slip faults which can generate big earthquakes such as 1976 Mw 6.5 Friuli Earthquake, 1998 and 2004 Bovec-Krn Earthquakes. The area is located between Austria, Slovenia and Italy. Our group, SEISRAM, has dense seismic station on the Italian part of the region and has access to get data from other countries on the region. We are monitoring the region with a good coverage by collaborating with other institutes on the Ce3RN project which we are also part of. We can detect lower than 0.5 Magnitude earthquakes. We use our database and other seismological centers to investigate the seismicity of the region between 1960 and 2016. Gutenberg-Richter magnitude frequency relationship is applied in order to get a knowledge about the seismicity of ..
Recurrent fault - valve behaviour detected by strain measurements in N - Adria
Full text linkWe analysed the data recorded by the NE-Italy tilt/strain gauges network in the time interval 1976-1996 (Braitenberg et al., 2006; 2019) at the light of the results of the analyses of Rossi et al. (2016; 2017; 2018) of the cGNSS at the northern tip of the Adria microplate. We considered the longest tiltmeter time series, in which long-term oscillations were previously observed (Rossi and Zadro, 1996). A transient oscillation appears to be present in the recordings of four tiltmeter sites, revealing a tilting along the tectonic features in the period 1984-1987. By using the same tomographic approach and the model of Rossi al. (2016; 2017), we located the transient’s source as originated in correspondence of the South Alpine thrust front, near its intersection with the Idrija fault, in western Slovenia, not far from the source identified by Rossi et al. (2016) for the 2006-2009 transient. The velocity field is compatibel with a fluid diffusion, confirmed by the results of the hydraulic tomographic inversion. The area, hence, would be confirmed as a source of fluid diffusion. The various thrusts and transpressive structures, involving formations with variable permeability, can act as barriers, generating overpressure conditions, and, from time to time, enable fluid diffusion in the surroundings. We calculated the fluid influx and the total discharge
Uncertainty budget of solid Earth data reductions to global gravity models
Full text linkSolid Earth applications of satellite gravity models commonly involve some type of data reduction - i.e. forward
modelling the gravity effect of known mass distributions to isolate an anomaly from the observed field, which is
then attributed to the enquired phenomenon. The adopted "known masses" suffer from the uncertainties arising
from the non-modelled variance in the shape of geological bodies and the density distribution therein. These
uncertainties are propagated to the reduced gravity field, superimposed to the formal errors provided with the
gravity model. Given the different origin between formal errors of satellite global gravity models (GGM), arising
from observation and noise models, and the contribution of geophysical data reductions, we aimed at assessing
the comprehensive error characteristics of reduced-GGMs.
In order to do so, we computed a set of common reductions (topography, crustal layers, mantle inhomogeneities)
using a combination of spectral- and space-domain forward modelling. Uncertainties in the input
quantities (depths and densities) were propagated trough Monte Carlo methods.
Geometries were constrained by a topography-bedrock-ice model (Earth2014), by a global layered model of the
lithosphere (LITHO1.0), and by local higher detail models of the crust and sediments, where available. Depth
uncertainties, if not provided with the input data, were assigned according to method-specific assumptions. Estimates of density and its variance come from probability distributions fitted to literature data, from petrophysical
relationships (e.g. velocity-composition-temperature) and from worst-case assumptions where no sufficient data is
available.
We report the outcome of a set of global models, at a resolution and spectral content coherent with the
currently available satellite-only GGMs. We resort to global uncertainty maps and to the familiar representations
employed in GGM sensitivity assessments (e.g. degree error curves). Different combinations of data reductions
were applied, simulating the interest in different anomalies (e.g. by correcting either for the crust or the mantle)
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