scholarly journals From fault creep to slow and fast earthquakes in carbonates

Geology ◽  
2019 ◽  
Vol 47 (8) ◽  
pp. 744-748 ◽  
Author(s):  
Franҫois X. Passelègue ◽  
Jérôme Aubry ◽  
Aurélien Nicolas ◽  
Michele Fondriest ◽  
Damien Deldicque ◽  
...  
Keyword(s):  
Seismic Waves ◽  
Central Italy ◽  
Confining Pressure ◽  
Mediterranean Area ◽  
Rupture Propagation ◽  
Fault Creep ◽  
Seismogenic Layer ◽  
Elastic Loading ◽  
High Frequency Seismic Waves ◽  
Hypocentral Location

Abstract A major part of the seismicity striking the Mediterranean area and other regions worldwide is hosted in carbonate rocks. Recent examples are the destructive earthquakes of L’Aquila (Mw 6.1) in 2009 and Norcia (Mw 6.5) in 2016 in central Italy. Surprisingly, within this region, fast (≈3 km/s) and destructive seismic ruptures coexist with slow (≤10 m/s) and nondestructive rupture phenomena. Despite its relevance for seismic hazard studies, the transition from fault creep to slow and fast seismic rupture propagation is still poorly constrained by seismological and laboratory observations. Here, we reproduced in the laboratory the complete spectrum of natural faulting on samples of dolostones representative of the seismogenic layer in the region. The transitions from fault creep to slow ruptures and from slow to fast ruptures were obtained by increasing both confining pressure (P) and temperature (T) up to conditions encountered at 3–5 km depth (i.e., P = 100 MPa and T = 100 °C), which corresponds to the hypocentral location of slow earthquake swarms and the onset of seismicity in central Italy. The transition from slow to fast rupture is explained by an increase in the ambient temperature, which enhances the elastic loading stiffness of the fault, i.e., the slip velocities during nucleation, allowing flash weakening and, in turn, the propagation of fast ruptures radiating intense high-frequency seismic waves.

scholarly journals An Italian Research Culture Collection of Wood Decay Fungi

Diversity ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 58 ◽  
Author(s):  
Carolina Elena Girometta ◽  
Annarosa Bernicchia ◽  
Rebecca Michela Baiguera ◽  
Francesco Bracco ◽  
Simone Buratti ◽  
...  
Keyword(s):  
Central Italy ◽  
Wood Decay ◽  
Mediterranean Area ◽  
Culture Collection ◽  
White Rot ◽  
Temperate Climate ◽  
Research Culture ◽  
Decay Fungi ◽  
Mn Peroxidase ◽  
The Mediterranean

One of the main aims of the University of Pavia mycology laboratory was to collect wood decay fungal (WDF) strains in order to deepen taxonomic studies, species distribution, officinal properties or to investigate potential applications such as biocomposite material production based on fungi. The Italian Alps, Apennines and wood plains were investigated to collect Basidiomycota basidiomata from living or dead trees. The purpose of this study was to investigate the wood decay strains of the Mediterranean area, selecting sampling sites in North and Central Italy, including forests near the Ligurian and Adriatic seas, or near the Lombardy lakes. The isolation of mycelia in pure culture was performed according to the current methodology and the identity of the strains was confirmed by molecular analyses. The strains are maintained in the Research Culture Collection MicUNIPV of Pavia University (Italy). Among the 500 WDF strains in the collection, the most interesting isolates from the Mediterranean area are: Dichomitus squalens (basidioma collected from Pinus pinea), Hericium erinaceus (medicinal mushroom), Inocutis tamaricis (white-rot agent on Tamarix trees), Perenniporia meridionalis (wood degrader through Mn peroxidase) and P. ochroleuca. In addition, strains of species related to the Mediterranean climate (e.g., Fomitiporia mediterranea and Cellulariella warnieri) were obtained from sites with a continental-temperate climate.

High frequency seismic waves and slab structures beneath Italy

2014 ◽  
Vol 391 ◽  
pp. 212-223 ◽  
Author(s):  
Daoyuan Sun ◽  
Meghan S. Miller ◽  
Nicola Piana Agostinetti ◽  
Paul D. Asimow ◽  
Dunzhu Li
Keyword(s):  
High Frequency ◽  
Seismic Waves ◽  
High Frequency Seismic Waves

Are Synthetic Accelerograms Suitable for Local Seismic Response Analyses at Near-Field Sites?

2021 ◽  
Author(s):  
Francesca Mancini ◽  
Sebastiano D’Amico ◽  
Giovanna Vessia
Keyword(s):  
Seismic Response ◽  
Seismic Waves ◽  
Near Field ◽  
Central Italy ◽  
Propagation Path ◽  
Soil Behavior ◽  
Seismic Stations ◽  
Seismic Input ◽  
Local Seismic Response ◽  
Finite Fault

ABSTRACT Local seismic response (LSR) studies are considerably conditioned by the seismic input features due to the nonlinear soil behavior under dynamic loading and the subsurface site conditions (e.g., mechanical properties of soils and rocks and geological setting). The selection of the most suitable seismic input is a key point in LSR. Unfortunately, few recordings data are available at seismic stations in near-field areas. Then, synthetic accelerograms can be helpful in LSR analysis in urbanized near-field territories. Synthetic accelerograms are generated by simulation procedures that consider adequately supported hypotheses about the source mechanism at the seismotectonic region and the wave propagation path toward the surface. Hereafter, mainshocks recorded accelerograms at near-field seismic stations during the 2016–2017 Central Italy seismic sequence have been compared with synthetic accelerograms calculated by an extended finite-fault ground-motion simulation algorithm code. The outcomes show that synthetic seismograms can reproduce the high-frequency content of seismic waves at near-field areas. Then, in urbanized near-field areas, synthetic accelerograms can be fruitfully used in microzonation studies.

scholarly journals Petrochirus sp. (Anomura, Paguroidea, Diogenidae) from the early Pleistocene of the Podere dell’Infrascato, Volterra (Pisa, Tuscany, central Italy)

2016 ◽  
Vol 3 (1) ◽  
pp. 66
Author(s):  
Giovanni Pasini ◽  
Alessandro Garassino
Keyword(s):  
Central Italy ◽  
Mediterranean Area ◽  
Early Pleistocene ◽  
Genus Distribution

We report <em>Petrochirus</em> sp. (Diogenidae Ortmann, 1892) from the early Pleistocene of the Podere dell’Infrascato, Volterra (Pisa, Tuscany, central Italy). The record of <em>Petrochirus</em> sp. in this peculiar environment (upper bathyal zone) is significant due to the scarce knowledge about the genus distribution in the paleo-Mediterranean area.

ANALYSIS OF THE DISTRIBUTION OF EPIPHYTIC LICHENS ON QUERCUS PUBESCENS ALONG AN ALTITUDINAL GRADIENT IN A MEDITERRANEAN AREA (TUSCANY, CENTRAL ITALY)

1997 ◽  
Vol 45 (1) ◽  
pp. 53-58 ◽  
Author(s):  
Stefano Loppi ◽  
Stergios Arg. Pirintsos ◽  
Vincenzo De Dominicis
Keyword(s):  
Altitudinal Gradient ◽  
Central Italy ◽  
Mediterranean Area ◽  
Multivariate Techniques ◽  
Epiphytic Lichens ◽  
Climatic Parameters ◽  
Quercus Pubescens ◽  
Epiphytic Lichen ◽  
The Core ◽  
Satellite Species

The distribution of epiphytic lichens on Quercus pubescens in Tuscany, central Italy, was studied by means of multivariate techniques along an altitudinal gradient from 0 to 900 m. Great differences in community structure were found and the altitude of 500 m was identified as an ecotone. Epiphytic lichen vegetation on trees below the ecotone varied significantly in relation to bark pH. Climatic parameters (temperature and rainfall) were probably related to altitude. Dust was probably responsible for the rise in bark pH. The distribution of lichen species in the sampling belts fitted the core-satellite hypothesis. The use of core and satellite species as biomonitors of air pollution and bioindicators of environmental conditions is discussed.

High‐frequency reflections in granite? Delineation of the weathering front in granodiorite at Piñon Flat, California

Geophysics ◽  
1999 ◽  
Vol 64 (6) ◽  
pp. 1828-1835 ◽  
Author(s):  
Stanley J. Radzevicius ◽  
Gary L. Pavlis
Keyword(s):  
High Frequency ◽  
Seismic Waves ◽  
Lower Layer ◽  
Specular Reflection ◽  
Earth Model ◽  
Remarkable Feature ◽  
Reflection Data ◽  
Weathered Layer ◽  
High Frequency Seismic Waves ◽  
Seismic Lines

We analyze data from two orthogonal seismic lines 336 m in length collected at Piñon Flat, California, over weathered granodiorite bedrock. Each line was made up of 10 reversed segments 84 m in length. We analyzed the first arrivals from these data and found dramatic variations in velocity along the profiles. An upper layer (approximately 2-m thick) known from trenching to be composed of soil and sandy grus had measured velocities ranging from 400 to 700 m/s. Velocities inferred from refraction analysis of first arrivals of the reversed lines revealed a heterogeneous lower layer below the soil with measured velocities of 1600–2700 m/s by a depth of 15 m. We interpret these data to be measuring velocities of a deeply weathered unit characterized by granodiorite corestones embedded in a matrix of saprolite. The most remarkable feature of these data emerged from attempting to process the same data as reflection data. Simple bandpass filtering in the 250–400 Hz band revealed a bright, impulsive arrival with three characteristic properties: (1) irregular velocity moveout that is inconsistent with that expected from a layered earth model, (2) the arrival is at a nearly constant time‐depth on all data, and (3) the arrival tends to be followed by a ringing coda whose frequency varies from trace to trace. This arrival ties exactly with a velocity discontinuity measured in a borehole located on one of the profiles that we interpret as the base of the weathered layer. We suggest this arrival is a specular reflection from a weathering front that occurs along horizontal sheeting joints at a fixed depth below the surface. This surface acts as an effective mirror for high‐frequency seismic waves which are then channeled upward through an intact, high-Q path of unaltered blocks of granodiorite to define the observed signals at the surface.

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