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  • 1
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    Fault Planes, Fault Zone Structure and Detachment Fragmentation Resolved With High‐Precision Aftershock Locations of the 2016–2017 Central Italy Sequence (2022)
    Wiley-AGU
    Details
    Publication Date: 2022-03-02
    Description: Three devastating earthquakes of MW ≥ 5.9 activated a complex system of high-angle normal, antithetic, and sub-horizontal detachment faults during the 2016–2017 central Italy seismic sequence. Waveform cross-correlation based double-difference location of nearly 400,000 aftershocks illuminate complex, fine-scale structures of interacting fault zones. The Mt. Vettore–Mt. Bove (VB) normal fault exhibits wide and complex damage zones, including a system of bookshelf faults that intersects the detachment zone. In the Laga domain, a comparatively narrow, shallow dipping segment of the deep Mt. Gorzano fault progressively ruptures through the detachment zone in four subsequent MW ∼ 5.4 events. Reconstructed fault planes show that the detachment zone is fragmented in four sub-horizontal, partly overlaying shear planes that correlated with the extent of the mainshock ruptures. We find a new, deep reaching seismic barrier that coincides with a bend in the VB fault and may play a role in controlling rupture evolution.
    Description: Published
    Description: e2021GL092918
    Description: 4T. Sismicità dell'Italia
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Machine-Learning-Based High-Resolution Earthquake Catalog Reveals How Complex Fault Structures Were Activated during the 2016–2017 Central Italy Sequence (2021)
    SSA
    Details
    Publication Date: 2021-12-17
    Description: The 2016–2017 central Italy seismic sequence occurred on an 80 km long normal‐fault system. The sequence initiated with the Mw 6.0 Amatrice event on 24 August 2016, followed by the Mw 5.9 Visso event on 26 October and the Mw 6.5 Norcia event on 30 October. We analyze continuous data from a dense network of 139 seismic stations to build a high‐precision catalog of ∼900,000 earthquakes spanning a 1 yr period, based on arrival times derived using a deep‐neural‐network‐based picker. Our catalog contains an order of magnitude more events than the catalog routinely produced by the local earthquake monitoring agency. Aftershock activity reveals the geometry of complex fault structures activated during the earthquake sequence and provides additional insights into the potential factors controlling the development of the largest events. Activated fault structures in the northern and southern regions appear complementary to faults activated during the 1997 Colfiorito and 2009 L’Aquila sequences, suggesting that earthquake triggering primarily occurs on critically stressed faults. Delineated major fault zones are relatively thick compared to estimated earthquake location uncertainties, and a large number of kilometer‐long faults and diffuse seismicity were activated during the sequence. These properties might be related to fault age, roughness, and the complexity of inherited structures. The rich details resolvable in this catalog will facilitate continued investigation of this energetic and well‐recorded earthquake sequence.
    Description: Published
    Description: 11–19
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: N/A or not JCR
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Implications of Receiver Plane Uncertainty for the Static Stress Triggering Hypothesis (2023)
    Wiley-AGU
    Details
    Publication Date: 2023-02-09
    Description: Static stress transfer from major earthquakes is commonly invoked as the primary mechanism for triggering aftershocks, but evaluating this mechanism depends on aftershock rupture plane orientations and hypocenter locations, which are often subject to significant observational uncertainty. We evaluate static stress change for an unusually large data set comprising hundreds to thousands of aftershocks following the 1997 Umbria-Marche, 2009 L’Aquila (Italy), and 2019 Ridgecrest (California) earthquake sequences. We compare failure stress resolved on aftershock focal mechanism planes and planes that are optimally oriented (OOPs) in the regional and earthquake perturbed stress field. Like previous studies, we find that failure stress resolved on OOPs overpredicts the percentage (〉70%) of triggered aftershocks relative to that predicted from observed aftershock rupture planes (∼50%–65%) from focal mechanisms solutions, independent of how nodal plane ambiguity is resolved. Further, observed aftershock nodal planes appear statistically different from OOPs. Observed rupture planes, at least for larger magnitude events (M 〉 3), appear to align more closely with pre-existing tectonic structures. The inferred observational uncertainty associated with nodal plane ambiguity, plane orientation, and, to second order, hypocentral location yields a broad range of aftershocks potentially triggered by static stress changes, ranging from slightly better than random chance to nearly any aftershock promoted, particularly those further than 5 km from the causative fault. Dynamic stresses, afterslip, pore fluids, and other sources of unresolved small-scale heterogeneity in the post-mainshock stress field may also contribute appreciably to aftershock occurrence closer to the mainshock
    Description: Published
    Description: e2021JB023589
    Description: 3T. Fisica dei terremoti e Sorgente Sismica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    On the Use of High-Resolution and Deep-Learning Seismic Catalogs for Short-Term Earthquake Forecasts: Potential Benefits and Current Limitations (2023)
    Wiley-AGU
    Details
    Publication Date: 2023-02-03
    Description: Enhanced earthquake catalogs provide detailed images of evolving seismic sequences. Currently, these data sets take some time to be released but will soon become available in real time. Here, we explore whether and how enhanced seismic catalogs feeding into established short-term earthquake forecasting protocols may result in higher predictive skill. We consider three enhanced catalogs for the 2016-2017 Central Italy sequence, featuring a bulk completeness lower by at least two magnitude units compared to the real-time catalog and an improved hypocentral resolution. We use them to inform a set of physical Coulomb Rate-and-State (CRS) and statistical Epidemic-Type Aftershock Sequence (ETAS) models to forecast the space-time occurrence of M3+ events during the first 6 months of the sequence. We track model performance using standard likelihood-based metrics and compare their skill against the best-performing CRS and ETAS models among those developed with the real-time catalog. We find that while the incorporation of the triggering contributions from new small magnitude detections of the enhanced catalogs is beneficial for both types of forecasts, these models do not significantly outperform their respective near real-time benchmarks. To explore the reasons behind this result, we perform targeted sensitivity tests that show how (a) the typical spatial discretizations of forecast experiments ( ≥ 2 km) hamper the ability of models to capture highly localized secondary triggering patterns and (b) differences in earthquake parameters (i.e., magnitude and hypocenters) reported in different catalogs can affect forecast evaluation. These findings will contribute toward improving forecast model design and evaluation strategies for next-generation seismic catalogs.
    Description: Published
    Description: e2022JB025202
    Description: 3T. Fisica dei terremoti e Sorgente Sismica
    Description: JCR Journal
    Keywords: Coulomb stress transfer; Epidemic‐Type Aftershock Sequence; high‐resolution seismic catalogs; operational earthquake forecasting; short‐term earthquake forecast
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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