scholarly journals The Imbricated Foreshock and Aftershock Activities of the Balsorano (Italy) Mw 4.4 Normal Fault Earthquake and Implications for Earthquake Initiation

2021 ◽  
Author(s):  
Hugo Sánchez-Reyes ◽  
David Essing ◽  
Eric Beaucé ◽  
Piero Poli
Keyword(s):  
Template Matching ◽  
Normal Fault ◽  
Spatiotemporal Patterns ◽  
Physical Processes ◽  
Aftershock Activity ◽  
Initiation Process ◽  
Before And After ◽  
Spatiotemporal Behavior ◽  
Triggering Mechanisms ◽  
Broadband Receivers

Abstract Foreshocks in the form of microseismicity are among the most powerful tools to study the physical processes that occur before main earthquakes. However, their detection and precise characterization is still sparse, especially for small-to-moderate-size earthquakes (Mw<6). We present here a detailed foreshock analysis for the 7 November 2019, Balsorano, Italy, normal fault earthquake (Mw 4.4). To improve the detection of the microseismicity before and after the mainshock, we use six three-component broadband receivers at distances of less than 75 km from the targeted seismicity, through template matching. To improve the understanding of the physical mechanism(s) behind the earthquake initiation process, as well as other accompanying phenomena, we also detail the spatiotemporal evolution of the sequence associated with this medium-sized earthquake, using waveform clustering and hypocenter relocation. Clear differences between foreshocks and aftershocks are revealed by this analysis. Moreover, five distinct spatiotemporal patterns associated with the different seismic activities are revealed. The observed spatiotemporal behavior shown by the foreshocks highlights a complex initiation process, which apparently starts on an adjacent unmapped antithetic fault. Finally, the aftershock activity comprises four different clusters with distinct spatiotemporal patterns, which suggests that the different clusters in this sequence have distinct triggering mechanisms.

A detailed study of the initiation process of a small (Mw4.4) normal fault earthquake in the middle lower crust

2020 ◽  
Author(s):  
Hugo Sanchez-Reyes ◽  
David Essing ◽  
Eric Beauce ◽  
Piero Poli
Keyword(s):  
Shear Stress ◽  
Lower Crust ◽  
Temporal Evolution ◽  
Normal Fault ◽  
Double Difference ◽  
Area Of Interest ◽  
Initiation Process ◽  
Aftershock Sequences ◽  
Before And After ◽  
Spatio Temporal

<p>Our knowledge about the physics behind the initiation process of large or small earthquakes remains limited. The current understanding of this process suggests that an earthquake occurs when increasing stress causes a pre-existing fault to fail suddenly (e.g. Dieterich 1992). Models such as the pre-slip instability growth or the triggered cascade of events have been proposed in order to theoretically explain this preparation stage (Dodge and Beroza, 1996; Ellsworth and Bullut, 2018; Bouchon et al., 2011). However, the mechanisms behind this process are still unknown. This debate is mainly due to the lack of direct observations of the subsurface shear stress evolution at the area of interest before and after an earthquake.</p><p>Considering that the shear stress evolves through time until the moment of failure, indirect observations of this change might be available but hidden inside the continuous seismic data. In this work, we analyze in detail the evolution of the seismic activity of a small (Mw 4.4) normal fault earthquake which occurred in Central Italy on 7th November 2019 at the middle lower crust (16 km depth). We first analyze the available continuous data using the Fast Matched Filter (Beauc\'e et al., 2017). Then, every new detected event is spatially localized with respect to the other events through the Double Difference algorithm (DD). As a result, we obtain the spatio-temporal evolution of the foreshock and aftershock sequences of that event.</p><p>The results from this analysis shed light on the patterns that the shear-stress spatio-temporal evolution follows before and after a given event. Therefore, we expect that this study will contribute to improve our understanding of the physics behind the earthquake initiation process.</p>

TIME AVERAGING OF IRREGULAR SPATIOTEMPORAL PATTERNS OF A LARGE APERTURE LASER IN TRANSITORY REGIME

2001 ◽  
Vol 11 (06) ◽  
pp. 1771-1779
Author(s):  
F. ENCINAS-SANZ ◽  
I. LEYVA ◽  
J. M. GUERRA
Keyword(s):  
Experimental Technique ◽  
Exposure Time ◽  
Time Integration ◽  
Spatiotemporal Patterns ◽  
Time Averaging ◽  
Bloch Equations ◽  
Ordered Structures ◽  
Large Aperture ◽  
Spatiotemporal Behavior ◽  
Maxwell Bloch Equations

By means of a new experimental technique, we measure quasi-intantaneous transverse intensity patterns in the gain-switch peak of a transversely excited atmospheric CO 2 laser with large aperture. The patterns recorded with a 2 ns resolution show a completely irregular spatiotemporal behavior, but when the exposure time of the measurements increases, boundary-determined ordered structures can be observed. As a quantification of this averaging process, the contrast of the intensity distributions decreases as the time integration grows. The results are numerically reproduced by integration of the full Maxwell–Bloch equations.

Aftershock Activity at Intermediate-Depth Earthquakes in Northern Chile Controlled by Plate Hydration

2020 ◽  
Author(s):  
Leoncio Cabrera ◽  
Sergio Ruiz ◽  
Piero Poli ◽  
Eduardo Contreras-Reyes ◽  
Renzo Mancini ◽  
...  
Keyword(s):  
Template Matching ◽  
Broad Band ◽  
Strong Motion ◽  
Seismic Source ◽  
Northern Chile ◽  
Aftershock Activity ◽  
Study Region ◽  
Abrupt Decrease ◽  
Intermediate Depth ◽  
The Impact

<p>We investigate the differences of the seismic source and aftershock activity using kinematic inversions and template matching respectively, for the six largest intraslab intermediate-depth earthquakes occurred in northern Chile (Mw ~6.3) since 2010 at depths between 90 and 130 km and recorded by dense strong-motion and broad-band seismic networks. In addition, we developed a thermal model using the finite element method in the study region with the aim of analyze the impact of temperature on seismic behavior as the oceanic plate subducts. Our results show that geometries of rupture zones are similar, with semi-axis for an elliptical patch approach about 5 km, and stress drop values between 7 and 30 MPa. On the other hand, the number of aftershocks exhibits clear differences, and their amount decreases with increasing the depth within the slab bounded by the 450 ºC isotherm, which represents a limit between a high-hydrated and a dry or low-hydrated region. Furthermore, mainshocks occur at distances from the top of the slab from 7 to 40 km, and all of them exhibit normal focal mechanisms suggesting that the extensional regimen deepens within the slab to the 700-750 ºC isotherm-depth. We suggest that in northern Chile the abrupt decrease of aftershocks in the lower part of the extensional regimen is caused by the absence of a hydrated slab at those depths.</p>

scholarly journals Integrative responses of neurons in nucleus tractus solitarius to visceral afferent stimulation and vestibular stimulation in vertical planes

2011 ◽  
Vol 301 (5) ◽  
pp. R1380-R1390 ◽  
Author(s):  
Yoichiro Sugiyama ◽  
Takeshi Suzuki ◽  
Vincent J. DeStefino ◽  
Bill J. Yates
Keyword(s):  
Copper Sulfate ◽  
Nucleus Tractus Solitarius ◽  
Vertical Plane ◽  
Vestibular Nuclei ◽  
Vestibular Stimulation ◽  
The Body ◽  
Head Movements ◽  
Intragastric Administration ◽  
Before And After ◽  
Triggering Mechanisms

Anatomical studies have demonstrated that the vestibular nuclei project to nucleus tractus solitarius (NTS), but little is known about the effects of vestibular inputs on NTS neuronal activity. Furthermore, lesions of NTS abolish vomiting elicited by a variety of different triggering mechanisms, including vestibular stimulation, suggesting that emetic inputs may converge on the same NTS neurons. As such, an emetic stimulus that activates gastrointestinal (GI) receptors could alter the responses of NTS neurons to vestibular inputs. In the present study, we examined in decerebrate cats the responses of NTS neurons to rotations of the body in vertical planes before and after the intragastric administration of the emetic compound copper sulfate. The activity of more than one-third of NTS neurons was modulated by vertical vestibular stimulation, with most of the responsive cells having their firing rate altered by rotations in the head-up or head-down directions. These responses were aligned with head position in space, as opposed to the velocity of head movements. The activity of NTS neurons with baroreceptor, pulmonary, and GI inputs could be modulated by vertical plane rotations. However, injection of copper sulfate into the stomach did not alter the responses to vestibular stimulation of NTS neurons that received GI inputs, suggesting that the stimuli did not have additive effects. These findings show that the detection and processing of visceral inputs by NTS neurons can be altered in accordance with the direction of ongoing movements.

scholarly journals Machine-Learning-Based High-Resolution Earthquake Catalog Reveals How Complex Fault Structures Were Activated during the 2016–2017 Central Italy Sequence

2021 ◽  
Vol 1 (1) ◽  
pp. 11-19
Author(s):  
Yen Joe Tan ◽  
Felix Waldhauser ◽  
William L. Ellsworth ◽  
Miao Zhang ◽  
Weiqiang Zhu ◽  
...  
Keyword(s):  
Central Italy ◽  
Normal Fault ◽  
Earthquake Sequence ◽  
Fault System ◽  
Earthquake Catalog ◽  
Earthquake Triggering ◽  
Aftershock Activity ◽  
Arrival Times ◽  
Complex Fault ◽  
Fault Structures

Abstract 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.

scholarly journals Temporal accuracy of human cortico-cortical interactions

2016 ◽  
Vol 115 (4) ◽  
pp. 1810-1820 ◽  
Author(s):  
Idan Tal ◽  
Moshe Abeles
Keyword(s):  
Cognitive Processes ◽  
Template Matching ◽  
Cognitive Process ◽  
Point Processes ◽  
Time Window ◽  
Spatiotemporal Patterns ◽  
Timing Accuracy ◽  
Synthetic Aperture Magnetometry ◽  
Better Than

The precision in space and time of interactions among multiple cortical sites was evaluated by examining repeating precise spatiotemporal patterns of instances in which cortical currents showed brief amplitude undulations. The amplitudes of the cortical current dipoles were estimated by applying a variant of synthetic aperture magnetometry to magnetoencephalographic (MEG) recordings of subjects tapping to metric auditory rhythms of drum beats. Brief amplitude undulations were detected in the currents by template matching at a rate of 2–3 per second. Their timing was treated as point processes, and precise spatiotemporal patterns were searched for. By randomly teetering these point processes within a time window W, we estimated the accuracy of the timing of these brief amplitude undulations and compared the results with those obtained by applying the same analysis to traces composed of random numbers. The results demonstrated that the timing accuracy of patterns was better than 3 ms. Successful classification of two different cognitive processes based on these patterns suggests that at least some of the repeating patterns are specific to a cognitive process.

scholarly journals Efficacy of StaMPS technique for monitoring surface deformation in L'Aquila, Italy

2014 ◽  
Vol XL-8 ◽  
pp. 141-145
Author(s):  
A. Tiwari ◽  
R. Dwivedi ◽  
A. B. Narayan ◽  
O. Dikshit ◽  
A. K. Singh
Keyword(s):  
Surface Deformation ◽  
Research Work ◽  
Normal Fault ◽  
Persistent Scatterer Interferometry ◽  
Persistent Scatterers ◽  
Time Period ◽  
Persistent Scatterer ◽  
Before And After ◽  
Movement Mechanism ◽  
Fault Mechanism

This research work investigates the efficacy of the Stanford Method for Persistent Scatterer Interferometry (StaMPS) in measuring the surface deformation over the L'Aquila region, Italy just before an event of earthquake of magnitude M<sub>w</sub> 6.3 by using seven descending Envisat C-Band ASAR images. The results show that the StaMPS technique successfully extracted sufficient number of Persistent Scatterers (PS) to derive a one dimensional (1D) time series displacement map which shows the deformation rates up to 59 mm/year in the satellite Line of Sight (LOS) direction and 50.8 mm/year in the direction opposite to the satellite LOS. Further, several deformation gradients are also observed from this map which indicate the occurrence of multiple crustal movement mechanism. Another dataset of 14 ASAR images is processed covering a time period before and after the earthquake in the study area to validate the results obtained by the previous dataset. We observed that the generated displacement map follows the deformation characteristics of the earlier displacement map in terms of magnitude and surface movement. We conclude that the generated displacement maps validate the presence of a normal fault mechanism with a tectonic process stretching in a NW-SE direction as predicted by earlier research studies.

Background Seismicity before and after the 1976 Ms 7.8 Tangshan Earthquake: Is Its Aftershock Sequence Still Continuing?

2020 ◽  
Author(s):  
Yue Liu ◽  
Jiancang Zhuang ◽  
Changsheng Jiang
Keyword(s):  
Aftershock Sequence ◽  
Tangshan Earthquake ◽  
Aftershock Activity ◽  
Background Rate ◽  
Epidemic Type Aftershock Sequence ◽  
Aftershock Sequences ◽  
Background Seismicity ◽  
Before And After ◽  
Large Earthquakes ◽  
Current Stage

Abstract The aftershock zone of the 1976 Ms 7.8 Tangshan, China, earthquake remains seismically active, experiencing moderate events such as the 5 December 2019 Ms 4.5 Fengnan event. It is still debated whether aftershock sequences following large earthquakes in low-seismicity continental regions can persist for several centuries. To understand the current stage of the Tangshan aftershock sequence, we analyze the sequence record and separate background seismicity from the triggering effect using a finite-source epidemic-type aftershock sequence model. Our results show that the background rate notably decreases after the mainshock. The estimated probability that the most recent 5 December 2019 Ms 4.5 Fengnan District, Tangshan, earthquake is a background event is 50.6%. This indicates that the contemporary seismicity in the Tangshan aftershock zone can be characterized as a transition from aftershock activity to background seismicity. Although the aftershock sequence is still active in the Tangshan region, it is overridden by background seismicity.

scholarly journals Functional Mapping before and after Low-Grade Glioma Surgery: A New Way to Decipher Various Spatiotemporal Patterns of Individual Neuroplastic Potential in Brain Tumor Patients

Cancers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2611 ◽  
Author(s):  
Hugues Duffau
Keyword(s):  
Structural Changes ◽  
Functional Neuroimaging ◽  
Functional Mapping ◽  
Spatiotemporal Patterns ◽  
Neurological Deficits ◽  
Low Grade ◽  
Postoperative Rehabilitation ◽  
Glioma Surgery ◽  
Preoperative Mapping ◽  
Before And After

Intraoperative direct electrostimulation mapping (DEM) is currently the gold-standard for glioma surgery, since functional-based resection allows an optimization of the onco-functional balance (increased resection with preserved quality of life). Besides intrasurgical awake mapping of conation, cognition, and behavior, preoperative mapping by means of functional neuroimaging (FNI) and transcranial magnetic stimulation (TMS) has increasingly been utilized for surgical selection and planning. However, because these techniques suffer from several limitations, particularly for direct functional mapping of subcortical white matter pathways, DEM remains crucial to map neural connectivity. On the other hand, non-invasive FNI and TMS can be repeated before and after surgical resection(s), enabling longitudinal investigation of brain reorganization, especially in slow-growing tumors like low-grade gliomas. Indeed, these neoplasms generate neuroplastic phenomena in patients with usually no or only slight neurological deficits at diagnosis, despite gliomas involving the so-called “eloquent” structures. Here, data gained from perioperative FNI/TMS mapping methods are reviewed, in order to decipher mechanisms underpinning functional cerebral reshaping induced by the tumor and its possible relapse, (re)operation(s), and postoperative rehabilitation. Heterogeneous spatiotemporal patterns of rearrangement across patients and in a single patient over time have been evidenced, with structural changes as well as modifications of intra-hemispheric (in the ipsi-lesional and/or contra-lesional hemisphere) and inter-hemispheric functional connectivity. Such various fingerprints of neural reconfiguration were correlated to different levels of cognitive compensation. Serial multimodal studies exploring neuroplasticity might lead to new management strategies based upon multistage therapeutic approaches adapted to the individual profile of functional reallocation.

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