scholarly journals Temporal Variability of Ground Shaking and Stress Drop in Central Italy: A Hint for Fault Healing?

2018 ◽  
Vol 108 (4) ◽  
pp. 1853-1863 ◽  
Author(s):  
Dino Bindi ◽  
Fabrice Cotton ◽  
Daniele Spallarossa ◽  
Matteo Picozzi ◽  
Eleonora Rivalta
Keyword(s):  
Temporal Variability ◽  
Stress Drop ◽  
Central Italy ◽  
Ground Shaking ◽  
Fault Healing

scholarly journals Exceedance of design actions in epicentral areas: insights from the ShakeMap envelopes for the 2016–2017 central Italy sequence

2021 ◽  
Author(s):  
Iunio Iervolino ◽  
Pasquale Cito ◽  
Chiara Felicetta ◽  
Giovanni Lanzano ◽  
Antonio Vitale
Keyword(s):  
Earthquake Engineering ◽  
Structural Damage ◽  
Structural Engineering ◽  
Central Italy ◽  
Civil Defense ◽  
Point Of View ◽  
Seismic Sequence ◽  
Ground Shaking ◽  
Motion Effect ◽  
Observed Damage

AbstractShakeMap is the tool to evaluate the ground motion effect of earthquakes in vast areas. It is useful to delimit the zones where the shaking is expected to have been most significant, for civil defense rapid response. From the earthquake engineering point of view, it can be used to infer the seismic actions on the built environment to calibrate vulnerability models or to define the reconstruction policies based on observed damage vs shaking. In the case of long-lasting seismic sequences, it can be useful to develop ShakeMap envelopes, that is, maps of the largest ground intensity among those from the ShakeMap of (selected) events of a seismic sequence, to delimit areas where the effects of the whole sequence have been of structural engineering relevance. This study introduces ShakeMap envelopes and discusses them for the central Italy 2016–2017 seismic sequence. The specific goals of the study are: (i) to compare the envelopes and the ShakeMap of the main events of the sequence to make the case for sequence-based maps; (ii) to quantify the exceedance of design seismic actions based on the envelopes; (iii) to make envelopes available for further studies and the reconstruction planning; (iv) to gather insights on the (repeated) exceedance of design seismic actions at some sites. Results, which include considerations of uncertainty in ShakeMap, show that the sequence caused exceedance of design hazard in thousands of square kilometers. The most relevant effects of the sequence are, as expected, due to the mainshock, yet seismic actions larger than those enforced by the code for structural design are found also around the epicenters of the smaller magnitude events. At some locations, the succession of ground-shaking that has excited structures, provides insights on structural damage accumulation that has likely taken place; something that is not accounted for explicitly in modern seismic design. The envelopes developed are available as supplemental material.

Stress Drop Derived from Spectral Analysis Considering the Hypocentral Depth in the Attenuation Model: Application to the Ridgecrest Region, California

2021 ◽  
Author(s):  
Dino Bindi ◽  
Hoby N. T. Razafindrakoto ◽  
Matteo Picozzi ◽  
Adrien Oth
Keyword(s):  
Stress Drop ◽  
Spectral Decomposition ◽  
Epicentral Distance ◽  
Source Parameters ◽  
S Wave ◽  
Qualitative Comparison ◽  
Ground Shaking ◽  
Attenuation Model ◽  
Hypocentral Distance ◽  
The Impact

ABSTRACT We investigate the impact of considering a depth-dependent attenuation model on source parameters assessed through a spectral decomposition. In particular, we evaluate the effect of considering the hypocentral depth as an additional variable for the attenuation model, using as the target the tendency of the average stress drop to increase with depth, as observed in recent studies. We analyze the Fourier spectra of S-wave windows for about 1900 earthquakes with a magnitude above 2.5 recorded in the Ridgecrest region, southern California. Two different parameterizations of the attenuation term are implemented in the spectral decomposition, either as a function of the hypocentral distance alone or as a function of both epicentral distance and depth. The comparison of the spectral attenuation curves shows that, although the hypocentral model describes, on average, the range of values spanned by the attenuation curve for different depths, systematic differences with distance, depth, and frequency are observed. These differences are transferred to the source spectra and, in turn, to the source parameters extracted from the best-fitting ω−2 models. In particular, stress drops for events deeper than 7 km are, on average, almost double even when depth is introduced explicitly in the attenuation model. The increase of stress drop with depth is confirmed also after accounting for the increase of the shear velocity with depth, which absorbs about 30%–40% of the total increase. Moreover, a qualitative comparison with a model for the gradient of the effective normal stress confirms the reliability of the observed trend. Finally, the coherent spatial patterns shown by a simplified 2D tomographic representation of the spectral residuals highlights the impact on ground-shaking variability of the lateral variability of the crustal attenuation properties in the region.

scholarly journals Basement Mapping of the Fucino Basin in Central Italy by ITRESC Modeling of Gravity Data

Geosciences ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 398
Author(s):  
Federico Cella ◽  
Rosa Nappi ◽  
Valeria Paoletti ◽  
Giovanni Florio
Keyword(s):  
Seismic Activity ◽  
Site Response ◽  
Gravity Data ◽  
A Priori ◽  
Central Italy ◽  
Gravity Anomalies ◽  
Gravity Modeling ◽  
Ground Shaking ◽  
Sedimentary Evolution ◽  
Fucino Basin

Sediments infilling in intermontane basins in areas with high seismic activity can strongly affect ground-shaking phenomena at the surface. Estimates of thickness and density distribution within these basin infills are crucial for ground motion amplification analysis, especially where demographic growth in human settlements has implied increasing seismic risk. We employed a 3D gravity modeling technique (ITerative RESCaling—ITRESC) to investigate the Fucino Basin (Apennines, central Italy), a half-graben basin in which intense seismic activity has recently occurred. For the first time in this region, a 3D model of the Meso-Cenozoic carbonate basement morphology was retrieved through the inversion of gravity data. Taking advantage of the ITRESC technique, (1) we were able to (1) perform an integration of geophysical and geological data constraints and (2) determine a density contrast function through a data-driven process. Thus, we avoided assuming a priori information. Finally, we provided a model that honored the gravity anomalies field by integrating many different kinds of depth constraints. Our results confirmed evidence from previous studies concerning the overall shape of the basin; however, we also highlighted several local discrepancies, such as: (a) the position of several fault lines, (b) the position of the main depocenter, and (c) the isopach map. We also pointed out the existence of a new, unknown fault, and of new features concerning known faults. All of these elements provided useful contributions to the study of the tectono-sedimentary evolution of the basin, as well as key information for assessing the local site-response effects, in terms of seismic hazards.

scholarly journals 2016–2017 Central Italy Earthquake Sequence: Seismic Retrofit Policy and Effectiveness

2018 ◽  
Vol 34 (4) ◽  
pp. 1671-1691 ◽  
Author(s):  
Silvia Mazzoni ◽  
Giulio Castori ◽  
Carmine Galasso ◽  
Paolo Calvi ◽  
Richard Dreyer ◽  
...  
Keyword(s):  
Earthquake Engineering ◽  
Central Italy ◽  
Companion Paper ◽  
Earthquake Sequence ◽  
Building Stock ◽  
Ground Shaking ◽  
Engineering Research ◽  
Central Italy Earthquake ◽  
Critical Facilities ◽  
The Impact

The 2016–2017 Central Italy earthquake sequence consisted of several moderately high-magnitude earthquakes, between M5.5 and M6.5, each centered in a different location and with its own sequences of aftershocks spanning several months. To study the effects of this earthquake sequence on the built environment and the impact on the communities, a collaborative reconnaissance effort was organized by the Earthquake Engineering Research Institute (EERI), the Eucentre Foundation, the European Centre for Training and Research in Earthquake Engineering (EUCentre), and the Rete dei Laboratori Universitari di Ingegneria Sismica (ReLuis). The effort consisted of two reconnaissance missions: one following the Amatrice Earthquake of 24 August 2016 and one after the end of the earthquake sequence, in May 2017. One objective of the reconnaissance effort was to evaluate existing strengthening methodologies and assess their effectiveness in mitigating the damaging effects of ground shaking. Parallel studies by the Geotechnical Extreme Events Reconnaissance (GEER) Association, presented in a companion paper, demonstrate that variations in-ground motions due to topographic site effects had a significant impact on damage distribution in the affected area. This paper presents that, in addition to these ground motion variations, variations in the vulnerability of residential and critical facilities were observed to have a significant impact on the level of damage in the region. The damage to the historical centers of Amatrice and Norcia will be used in this evaluation: the historical center of Amatrice was devastated by the sequence of earthquakes; the significant damage in Norcia was localized to individual buildings. Amatrice has not experienced the same number of devastating earthquakes as Norcia in the last 150 years. As a result, its building stock is much older than that of Norcia and there appeared to be little visual evidence of strengthening of the buildings. The distribution of damage observed throughout the region was found to be indicative of the effectiveness of strengthening and of the need for a comprehensive implementation of retrofit policies.

scholarly journals Earthquake Seismic Moment, Rupture Radius and Stress-drop from P-wave Displacement Amplitude vs Time Curves

2021 ◽  
Author(s):  
aldo zollo ◽  
sahar nazeri ◽  
Simona Colombelli
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Central Italy ◽  
Average Stress ◽  
Displacement Amplitude ◽  
P Wave ◽  
Parametric Modelling ◽  
Peak Displacement ◽  
Reliable Determination ◽  
Anelastic Attenuation

The reliable determination of earthquake source parameters is a relevant task of seismological investigations which ground nowadays on high quality seismic waveforms collected by near-source dense arrays of ground motion sensors. Here we propose a parametric modelling technique which analyzes the time-domain P-wave signal recorded in the near-source range of small-to-large size earthquakes. Assuming a triangular moment-rate function and a uniform speed, circular rupture model, we develop the equations to estimate the seismic moment, rupture radius and stress-drop from the corner-time and plateau level of the average logarithm of the P-wave displacement vs time curves (LPDT). The constant-Q, anelastic attenuation effect is accounted by a post-processing procedure that evaluates the Q-unperturbed moment-rate triangular shape.<br>The methodology has been validated through the application to the acceleration records of the 2016-2017 Central Italy and 2007-2019 Japan earthquake sequences covering a wide moment magnitude range (Mw 2.5 - 6.5) and recording distance < 100 km. After correcting for the anelastic attenuation function, the estimated average stress-drop and the confidence interval (〈∆σ〉=0.60 (0.42-0.87) MPa and 〈∆σ〉=1.53 (1.01-2.31) for crustal and subcrustal events of Japan and 〈∆σ〉=0.36(0.30-0.44) MPa for Central Italy) show, for both regions, a self-similar, constant stress-drop scaling of the rupture duration/radius with seismic moment. The smaller sensitivity of the spatially averaged, time-varying peak displacement amplitude to the radiation from localized high slip patch on the fracture surface, could explain the retrieved smaller average stress-drops for sub-crustal earthquakes in Japan and M>5.5 events in Central Italy relative to previous estimates using spectral methods.<br><br>

Fusing Damage Proxy Maps with Geospatial Models for Bayesian Updating of Seismic Ground Failure Estimations: A Case Study in Central Italy

2021 ◽  
Author(s):  
Susu Xu ◽  
Joshua Dimasaka ◽  
David J. Wald ◽  
Hae Young Noh
Keyword(s):  
False Alarm ◽  
Environmental Changes ◽  
Central Italy ◽  
Bayesian Updating ◽  
Building Damage ◽  
Remotely Sensed Data ◽  
Ground Shaking ◽  
Ground Failure ◽  
Causal Graph

&lt;p&gt;On August 24, 2016, a magnitude-6.2 earthquake in Central Italy resulted in at least 290 deaths, significant ground failure (including landslides and liquefaction), and building damage. After the event, the NASA Advanced Rapid Imaging and Analysis team produced Damage Proxy Maps (DPM) that reflect earthquake-induced surficial changes using synthetic aperture data from the COSMO-SkyMed satellite. However, exact causes of these surface changes, e.g., ground failure, building damage, or other environmental changes, are difficult to directly differentiate from the satellite images alone. For example, changes could reflect building damage, landslides, the co-occurrence of both, or numerous other processes that are not related to the earthquake. Alternatively, existing ground failures models are useful in locating areas of higher likelihoods but suffer from high false alarm rates due to inaccurate or incomplete geospatial proxies and complex physical interdependencies between shaking and specific sites of ground failure. In this work, we present a joint Bayesian updating framework using a causal graph strategy. The Bayesian causal graph models physical interdependencies among ground shaking, ground failures, building damage, and remote sensing observations. Based on the graph, a variational inference approach is designed to jointly update the estimates of ground failure and building damage through fusing traditional geospatial models and the remotely sensed data. As a case study, the DPMs in Central Italy are input to the model for jointly calibrating and updating the probability of ground failure estimations as well as for estimating building damage probabilities. The results showed that by incorporating high-resolution imagery, our model significantly reduces the false alarm rate of ground failure estimates and improves the spatial accuracy and resolution of ground failure and building damage inferences.&lt;/p&gt;

Fault healing plays a key role in creating the spectrum of tectonic faulting styles from seismic to aseismic slip

2020 ◽  
Author(s):  
Chris Marone
Keyword(s):  
Potential Energy ◽  
Stress Drop ◽  
Elastic Strain ◽  
Stability Boundary ◽  
Fault Slip ◽  
Slow Slip ◽  
Stick Slip ◽  
Slow Earthquakes ◽  
The Stability ◽  
Fault Healing

&lt;p&gt;Tectonic faults fail in a broad spectrum of modes ranging from aseismic creep to fast, ordinary, earthquakes modulated by elastodynamic rupture processes. Laboratory friction experiments with repetitive stick-slip failure have reproduced this complete range of modes with failure durations spanning several orders of magnitude. These works show that the frictional weakening rate with slip (i.e., the rheological critical stiffness &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt; =&amp;#963;&lt;sub&gt;n&lt;/sub&gt;(b-a)/D&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt;, where &lt;em&gt;&amp;#963;&lt;sub&gt;n&lt;/sub&gt;&lt;/em&gt;&amp;#160;is effective fault normal stress, &lt;em&gt;D&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt; is the friction critical slip distance and &lt;em&gt;(b-a)&lt;/em&gt; represents the friction rate parameter) is the primary control on the mode of slip, but higher-order effects are also important including variation of &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt; &amp;#160;&lt;/em&gt;with slip velocity.&amp;#160; Far from the stability boundary, stick-slip occurs when the rate of elastic unloading with slip &lt;em&gt;k&lt;/em&gt; is small compared to the frictional weakening rate (i.e., &lt;em&gt;k&lt;/em&gt;&lt;&lt;&lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt;). Potential energy, in the form of stored elastic strain, drives rapid fault acceleration. Near the stability boundary, when &lt;em&gt;k ~ k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt;, lab experiments document slow and quasi-dynamic failure events, consistent with the observation that earthquake stress drop is negligible for slow earthquakes. Lab data show that stick-slip stress drop decreases systematically as &lt;em&gt;k/k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt; approaches 1 from below. There are two possible scenarios for slow slip near the stability boundary, although they are degenerate in most cases. 1) Fault slip relieves elastic stresses prior to failure and thus the potential energy needed to drive fast rupture is absent. 2) Elastic strain accumulates but the fault rheology is velocity strengthening or otherwise inconsistent with rapid slip, for example because the frictional weakening rate &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt;&amp;#160; is low. &amp;#160;In Scenario 1, slip can occur early in the seismic cycle, as creep, or later in the cycle when shear stress reaches a critical value for precursory slip. &amp;#160;In either case, slip occurs because the rate of fault healing is low compared to the stressing rate. A low rate of fault healing can also explain Scenario 2 because the friction state evolution parameter &lt;em&gt;b&lt;/em&gt; scales directly with the rate of fault healing and &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt;. Given that the friction parameter &lt;em&gt;a&lt;/em&gt; is positive definite, the frictional healing rate (&lt;em&gt;b&lt;/em&gt;) sets the scale of &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt; for a given value of &lt;em&gt;D&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt;. Thus, while these two scenarios for slow slip appear distinct they both derive from the rate of fault healing.&amp;#160; Exceptions would involve faults that are strongly velocity weakening &lt;em&gt;(b-a)&lt;/em&gt; &gt;&gt;0 yet have negligible healing rates (&lt;em&gt;b&lt;/em&gt; ~ 0), which is indeed rare.&amp;#160; The rate of fault healing is expected to vary with mineralogy, effective stress, temperature and other factors. Thus, while we expect a systematic variation of seismic style with depth, associated with changes in &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt;, we should not be surprised to find a spectrum of faulting styles throughout the lithosphere, including a range of styles at a given location.&amp;#160; Discoveries of seismic tremor, low frequency earthquakes, and other modes of fault slip are challenging our views of tectonic faulting and they highlight the need for close connections between field observations, detailed laboratory work and theoretical studies of friction and faulting.&lt;/p&gt;

scholarly journals Engineering-Geological Features Supporting a Seismic-Driven Multi-Hazard Scenario in the Lake Campotosto Area (L’Aquila, Italy)

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 107
Author(s):  
Benedetta Antonielli ◽  
Francesca Bozzano ◽  
Matteo Fiorucci ◽  
Salomon Hailemikael ◽  
Roberto Iannucci ◽  
...  
Keyword(s):  
Hazard Analysis ◽  
Central Italy ◽  
Holistic Approach ◽  
Disaster Mitigation ◽  
Ground Shaking ◽  
Geological Features ◽  
Geologic Hazards ◽  
Seismic Amplification ◽  
Hazard Scenario ◽  
Using Data

This paper aims to describe the seismic-driven multi-hazard scenario of the Lake Campotosto artificial basin (Abruzzo Region, Central Italy), and it can represent a preparatory study for a quantitative multi-hazard analysis. A comprehensive multi-hazard scenario considers all the effects that can occur following the base ground shaking, providing a holistic approach to assessing the real hazard potential and helping to improve management of disaster mitigation. The study area might be affected by a complex earthquake-induced chain of geologic hazards, such as the seismic shaking, the surface faulting of the Gorzano Mt. Fault, which is very close to one of the three dams that form the Lake Campotosto, and by the earthquake-triggered landslides of different sizes and typologies. These hazards were individually and qualitatively analyzed, using data from an engineering-geological survey and a geomechanical classification of the rock mass. With regard to the seismic shaking, a quantitative evaluation of the seismic response of the Poggio Cancelli valley, in the northern part of Lake Campotosto, was performed, highlighting different seismic amplification phenomena due to morphologic and stratigraphic features. Some insights about the possible multi-hazard approaches are also discussed.

Sign in / Sign up

Export Citation Format

Share Document