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  • 1
    Publication Date: 2022-02-11
    Description: Abstract
    Description: Here we report the raw data of the friction experiments carried out on basalt-built simulated faults defined by rock-on-rock contacts and powdered gouge. The experiments were specifically designed to investigate the role of fault microstructure on the frictional properties of basalts and the fault slip stability, and were conducted with the rotary-shear apparatus (SHIVA) and the biaxial deformation apparatus (BRAVA), hosted at the National Institute of Geophysics and Volcanology (INGV) in Rome. Simulated faults were sheared at constant normal stress from 4 to 30 MPa. In SHIVA experiments, we deformed samples at constant slip velocity of 10 μm/s up to 56 mm net slip. In BRAVA tests we performed a sequence of velocity steps (0.1 to 300 μm/s), followed by slide-hold-slide tests (30-3000 s holds; V=10 μm/s slides). Our main results highlight the frictionally strong nature of basalt faults and show opposite friction velocity dependence upon the velocity upsteps: while fault gouges exhibit velocity weakening behavior with increasing normal stress and sliding velocity, bare rock surfaces transition to velocity strengthening behavior as we approach higher slip velocities. The experiments setup and data are further described in the manuscript “Frictional properties of basalt experimental faults and implications for volcano-tectonic settings and geo-energy sites” to which these data are supplementary material.
    Keywords: Fault mechanics ; Friction of basalts ; Rate and State Friction ; Bare rock surfaces ; Simulated fault gouge ; EPOS ; multi-scale laboratories ; rock and melt physical properties ; alkali-olivine_basalt ; Biaxial ; Friction ; Rotary Shear ; Strain gauge
    Type: Dataset , Dataset
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  • 2
    Publication Date: 2021-01-25
    Description: Tectonic pseudotachylytes are solidified frictional melts produced on faults during earthquakes and are robust markers of seismic slip events. Nonetheless, pseudotachylytes are apparently uncommon fault rocks, because they are either rarely produced or are easily lost from the geological record. To solve this conundrum, long-lasting (18–35 days) hydrothermal alteration tests were performed on fresh pseudotachylytes produced by sliding solid rock samples at seismic slip rates in the laboratory. After all tests, the pseudotachylytes were heavily altered with dissolution of the matrix and neo-formation of clay aggregates. Post-alteration products closely resemble natural altered pseudotachylytes and associated ultracataclasites (i.e., fault rocks affected by fracturing in the absence of melting), demonstrating that the preservation potential of original pseudotachylyte microstructures is very short, days to months, in the presence of hydrothermal fluids. As a consequence, pseudotachylytes might be significantly underrepresented in the geological record, and on-fault frictional melting during earthquakes is likely to occur more commonly than generally believed
    Description: ERC CoG NOFEAR 614705
    Description: Published
    Description: e2020GL090020
    Description: 3T. Sorgente sismica
    Description: JCR Journal
    Keywords: Fault ; Earthquakes ; Pseudotachylyte ; Earthquake mechanics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2021-01-18
    Description: N.B. L'articolo inizia alla pagina 10 del file PDF. E' preceduto dall'indice degli altri articoli che compaiono su quel volume della rivista.
    Description: Con un accordo tra INGV e SSI (progetto IPODATA) è stata installata strumentazione sismica in cavità artificiali, fin dal 2007. In seguito, in alcuni siti ipogei, si è installata nuova strumentazione geofisica come segue: - nel bunker all’interno del Monte Soratte, presso S. Oreste (RM), è ora attivo un impianto di monitoraggio delle onde elettromagnetiche a bassissima frequenza (banda VLF) ed, associato, un misuratore di radon, il tutto per lo studio di potenziali precursori sismici; - grazie ad una collaborazione tra INGV, UnivAQ e INFN, in un sondaggio orizzontale degli anni ’80, vicino ai laboratori del Gran Sasso (LNGS), sono dal 2015 in registrazione continua (20 sps) sensori di pressione e di conducibilità dell’acqua sotterranea. Durante la sequenza sismica di Amatrice (Mw=6.0, 24/08/2016), i dati di pressione hanno mostrato chiare anomalie circa 5 giorni prima del terremoto; -infine alcuni cambiamenti hanno riguardato altri siti IPODATA (PTRJ, CESX ecc.). ABSTRACT: Following the agreement between INGV and SSI (IPODATA project), seismic equipment was installed in artificial cavities, starting from 2007. Later, in some sites, new geophysical instrumentation was installed in addition, as follows: - in the bunker inside Monte Soratte, near S. Oreste (RM), a monitoring system for very low frequency electromagnetic waves (VLF) has been recently installed together with a radon meter, both for the study of potential seismic precursors; - since 2015, according to a collaboration between INGV, UnivAQ and INFN, in a horizontal borehole drilled (in the ’80s) next to the deep underground laboratories of Gran Sasso (LNGS), pressure and conductivity of groundwater have been recorded by sensors in continuous high sampling (20 sps); during the Amatrice seismic sequence (08/24/2016, Mw=6.0) the pressure data showed clear anomalies about 5 days before the earthquake; - finally, upgrades were carried out in other IPODATA sites (PTRJ, CESX etc.)
    Description: - Societa Speleologia Italiana - Commissione Nazionale Cavita' Artificiali - INGV - Universita' degli studi di Palermo, Dipartimento di Scienze della Terra e del Mare (DiSTeM) - Federazione Speleologica Regionale Siciliana (FSRS) - HYPOGEA - SIGEA (Societa' Italiana di Geologia Ambientale)
    Description: Published
    Description: 207-214
    Description: 1IT. Reti di monitoraggio e sorveglianza
    Description: N/A or not JCR
    Keywords: Cavita' artificiali ; stazione sismica ; precursori sismici / seismic precursors ; VLF band ; radon ; ipogei ; rumore sismico / seismic noise ; artificial cavities ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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