Precursory slow-slip loaded the 2009 L'Aquila earthquake sequence

Borghi, Alessandra; Aoudia, Abdelkrim; Javed, Faisal; Barzaghi, Riccardo

doi:10.1093/gji/ggw046

Cited by 44 publications

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“…While the precursory moment release remains scarcely determined in most natural seismicity, several examples of well‐instrumented earthquakes seem to follow the same trend as our laboratory earthquakes and highlight that the M p scales with the seismic moment of the mainshock (Figure ). Note that we tried to compile as many observations as possible (to our knowledge) where the precursory nucleation phase could be resolved using geodetic analyses of modeled fault displacement prior to the mainshock (Borghi et al, ., Kato et al, , Socquet et al, ; Radiguet et al, ; Ruiz et al, ; Graham et al, ; Voss et al, ) and/or aseismic fault slip inferred from earthquake repeaters and foreshocks (Bouchon et al, ; Huang & Meng, ; Kato et al, ; Kato et al, ; Ruiz et al, ). Therefore, Figure (details in Item S3) should be considered carefully.…”

Section: Discussionmentioning

confidence: 99%

Can Precursory Moment Release Scale With Earthquake Magnitude? A View From the Laboratory

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Schubnel

et al. 2019

Geophysical Research Letters

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Today, earthquake precursors remain debated. While precursory slow slip is an important feature of earthquake nucleation, foreshock sequences are not always observed, and their temporal evolution remains poorly constrained. We report on laboratory earthquakes conducted under upper‐crustal stress and fluid pressure conditions. The dynamics of precursors (slip, seismicity, and fault coupling) prior to the mainshock are dramatically affected by slight changes in fault conditions (fluid pressure and slip history). A relationship between precursory moment release and mainshock magnitude is systematically observed, independent of fault conditions. Based on nucleation theory, we derive a semiempirical scaling relationship which explains this trend for laboratory earthquakes. Several natural observations of earthquakes ranging from ~Mw 6.0–9.0, where precursory moment release could be estimated, seem to follow the extrapolation of the laboratory‐derived scaling law. Notwithstanding spatiotemporal complexity in natural seismicity, some moderate to large earthquake magnitudes might be estimated through integrated seismological and geodetic measurements of both seismic and aseismic slips during nucleation.

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Section: Discussionmentioning

confidence: 99%

Can Precursory Moment Release Scale With Earthquake Magnitude? A View From the Laboratory

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Schubnel

et al. 2019

Geophysical Research Letters

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“…The AQE largest aftershock, for example, Ocre, nucleated on such ramp at a depth of about 14 km. A slow‐slip seismic event, precursory of AQE, nucleated on the horizontal flat, on 12 February 2009 (Borghi et al, ).…”

Section: Three‐dimensional Modelingmentioning

confidence: 99%

Coseismic Stress and Strain Field Changes Investigation Through 3‐D Finite Element Modeling of DInSAR and GPS Measurements and Geological/Seismological Data: The L'Aquila (Italy) 2009 Earthquake Case Study

et al. 2018

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We investigate the L'Aquila 2009 earthquake (AQE, Mw 6.3, Italy) through a 3‐D Finite Element (FE) mechanical model based on the exploitation of ENVISAT DInSAR and GPS measurements and an independently generated fault model. The proposed approach mainly consists of (a) the generation of a 3‐D fault model of the active structures involved in the sequence and those neighboring to them, benefiting of a large geological and seismological data set; (b) the implementation of the generated 3‐D fault model in a FE environment, by exploiting the elastic dislocation theory and considering the curved fault geometry and the crustal heterogeneities information; and (c) the optimization of the seismogenic crustal blocks model parameters in order to reproduce the geodetic measurements. We show that our modeling approach allows us to well reproduce the coseismic surface displacements, including their significant asymmetric pattern, as shown by the very good fit between the modeled ground deformations and the geodetic measurements. Moreover, a comparative analysis between our FE model results and those obtained by considering a classical analytical (Okada) model, for both the surface displacements and the Coulomb stress changes, has been performed. Our model permits to investigate the coseismic stress and strain field changes relevant to the investigated volume and their relationships with the surrounding geological structures; moreover, it highlights the very good correlation with the seismicity spatial distribution. The retrieved stress field changes show different maxima: (a) at few kilometers depth, within the main event surface rupture zone; (b) at depths of 5–9 km in correspondence of main event hypocentral area, along the SW dipping Paganica Fault System (PFS); and (c) at depths of 12–14 km, in correspondence of the largest aftershock hypocentral area, along a steep segment of an underlying east dipping basal detachment. Moreover, the main event hypocenter is localized in a region of high‐gradient strain field changes, while a deeper volumetric dilatation lobe involves the largest aftershock zone. From these findings, we argue that the AQE hanging wall downward movement along the steep portion of PFS might have been modulated by the underlying basal detachment; on the other hand, the coseismic eastward motion of the PFS footwall might have triggered further slip on the OS, thus releasing the largest aftershock on an independent source. The retrieved stress and strain field changes, which support the active role of the OS, have been also validated through a comparative analysis with those obtained from independent geological, seismological, and GPS measurements.

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“…For example, the seismicity in the Gulf of Corinth is mainly characterized by swarms (Duverger et al, ), with large and damaging earthquakes occasionally (e.g., M~6 Aigion earthquake, Bernard et al, ). The l'Aquila earthquake (Mw = 6.2, 2009, central Italy) occurred after a 2‐month‐long swarm‐like crisis, interpreted as driven by a slow‐slip event (Borghi et al, ). Therefore, in order to understand the overall behavior of a seismic area, it is of crucial importance to understand what the driving processes are and how they interact.…”

Section: Introductionmentioning

confidence: 99%

Fluid‐Induced Swarms and Coseismic Stress Transfer: A Dual Process Highlighted in the Aftershock Sequence of the 7 April 2014 Earthquake (Ml 4.8, Ubaye, France)

et al. 2019

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The upper part of the Ubaye Valley (French Alps) is characterized by alternating mainshock-aftershock sequences and swarms. Particularly, during the 2012-2015 crisis, four mainshocks with Ml > 3.5 occurred. We here focus on the aftershocks of the largest one (Ml = 4.8, 7 April 2014), in order to better understand the involved processes behind this peculiar seismic behavior. We use template matching detection, waveform classification, and double-difference relocations to analyze this seismicity, on average and at the scale of the clusters that compose it. Most event sources are aligned along a plane consistent with the mainshock fault (N165, 65°W), but occurred on conjugate structures. A few clusters of seismicity are also observed far from the mainshock source. Our analysis shows that distinct, spatially separated processes are at play. While coseismic stress transfer explains the seismicity close to the mainshock source, fluid-pressure diffusion and distant stress triggering are required to generate events farther away. The overall distributions in time and magnitude followed a slow Omori's decay and a Gutenberg-Richter relationship, respectively. However, these classical responses arise from the superposition of very different behaviors, associated with different processes at depth.Plain Language Summary Earthquakes have regularly shaken the upper part of the Ubaye valley, near the town of Barcelonnette in the Southwestern French Alps, for nearly 20 years. The earthquake behavior is peculiar, as swarms of numerous low magnitude events alternate with larger earthquakes, such as the Ml 4.8 one occurring on 7 April 2014. To understand this dual behavior, we performed an in-depth analysis of the aftershock of this event. The seismicity mainly aligns on a plane consistent with the mainshock fault (N165, 65°W). However, most of the events occurred on branching structures, belonging to the damaged zone of this fault, or on some other small faults far away. While the average behavior of this aftershock sequence is close to a standard one, we show that two different processes occurred at depth. Events occurring close to the mainshock are triggered by coseismic stress transfer, while fluid-pressure diffusion are likely required to explain the seismicity further away. Such dual process should be considered for seismic hazard assessment.

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Precursory slow-slip loaded the 2009 L'Aquila earthquake sequence

Cited by 44 publications

References 36 publications

Can Precursory Moment Release Scale With Earthquake Magnitude? A View From the Laboratory

Can Precursory Moment Release Scale With Earthquake Magnitude? A View From the Laboratory

Coseismic Stress and Strain Field Changes Investigation Through 3‐D Finite Element Modeling of DInSAR and GPS Measurements and Geological/Seismological Data: The L'Aquila (Italy) 2009 Earthquake Case Study

Fluid‐Induced Swarms and Coseismic Stress Transfer: A Dual Process Highlighted in the Aftershock Sequence of the 7 April 2014 Earthquake (Ml 4.8, Ubaye, France)

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