scholarly journals Bayesian analysisof a probability distribution for local intensity attenuation

2009 ◽  
Vol 47 (5) ◽  
Author(s):  
R. Rotondi ◽  
G. Zonno
Keyword(s):  
Epicentral Distance ◽  
Central Italy ◽  
Random Variable ◽  
Macroseismic Intensity ◽  
Propagation Path ◽  
Physical Parameters ◽  
Intensity Attenuation ◽  
Data Points ◽  
Local Intensity ◽  
Intensity Decay

Intensity attenuation and its variation as a function of the distance and earthquake size is still a critical issue in evaluating seismic hazard. We present a method that allows us to incorporate additional information from the historical earthquake felt reports in the probability estimation of local intensity attenuation. The approach is based on two ideas: a) standard intensity versus epicentral distance relationships constitute an unnecessary filter between observations and estimates; and b) the intensity decay process is affected by many, scarcely known elements (the physical parameters of the source, propagation path effects, building vulnerability, the semi-qualitative character of macroseismic scales, etc.). Hence intensity decay should be treated as a random variable as is the macroseismic intensity. We assume here that decay, defined on the set {0,1, ..., I0}, follows a binomial distribution with parameters (I0, p); p depends on the distance from the epicenter and is related to the probability of null decay at that distance. According to the Bayesian approach this p parameter is, in turn, a Beta random variable. The observations related to earthquakes with their epicenter outside the area concerned, but belonging to homogeneous zones, are used as prior knowledge of the phenomenon, while the data points of events inside the area are used to update the estimates through the posterior means of the quantities involved. Our methodology is described in detail in an application to the Umbria-Marche area in Central Italy. The data sets examined are the macroseismic intensity database DOM4.1 and the zonation ZS.4, both compiled by the Italian Group for Defence against Earthquakes (GNDT). The method is validated by comparing the observed and the estimated intensity data points of the Camerino (28/07/1799) and of the Colfiorito (26/09/1997) earthquakes.

Macroseismic intensity versus epicentral distance: the case of Central Italy

1991 ◽  
Vol 193 (1-3) ◽  
pp. 165-171 ◽  
Author(s):  
G. Grandori ◽  
A. Drei ◽  
F. Perotti ◽  
A. Tagliani
Keyword(s):  
Epicentral Distance ◽  
Central Italy ◽  
Macroseismic Intensity

scholarly journals An analytic method for separating local from regional effects on macroseismic intensity

1995 ◽  
Vol 38 (1) ◽  
Author(s):  
P. Tosi ◽  
V. De Rubeis ◽  
C. Gasparini
Keyword(s):  
Macroseismic Intensity ◽  
Analytic Method ◽  
Macroseismic Data ◽  
Regional Trend ◽  
Regional Effects ◽  
Republic Of Macedonia ◽  
Macroseismic Field ◽  
Qualitative Nature ◽  
Local Intensity ◽  
Yugoslavian Republic

nterpretation of macroseismic data is hazardous, due to its qualitative nature. This, linked with errors in eval- uation,) and the variations of local intensity, makes it difficult to draw valid conclusions. This study presents a statistical method as the basis for distinguishing the diverse components that constitute a macroseismic field. The method is based on the polar transformation of the coordinate system and on the analysis of the fractal di- mension of the intensity values, exposed to the gradually increasing action of a two-dimensional filter. The fractal dimension is shown to be an ideaI parameter with which to measure out the filtering process in order to separate the local components from the regional trend. This method has been applied to two Italian events and to an earthquake which took pIace in the Former Yugoslavian Republic of Macedonia (FYROM).

Are Synthetic Accelerograms Suitable for Local Seismic Response Analyses at Near-Field Sites?

2021 ◽  
Author(s):  
Francesca Mancini ◽  
Sebastiano D’Amico ◽  
Giovanna Vessia
Keyword(s):  
Seismic Response ◽  
Seismic Waves ◽  
Near Field ◽  
Central Italy ◽  
Propagation Path ◽  
Soil Behavior ◽  
Seismic Stations ◽  
Seismic Input ◽  
Local Seismic Response ◽  
Finite Fault

ABSTRACT Local seismic response (LSR) studies are considerably conditioned by the seismic input features due to the nonlinear soil behavior under dynamic loading and the subsurface site conditions (e.g., mechanical properties of soils and rocks and geological setting). The selection of the most suitable seismic input is a key point in LSR. Unfortunately, few recordings data are available at seismic stations in near-field areas. Then, synthetic accelerograms can be helpful in LSR analysis in urbanized near-field territories. Synthetic accelerograms are generated by simulation procedures that consider adequately supported hypotheses about the source mechanism at the seismotectonic region and the wave propagation path toward the surface. Hereafter, mainshocks recorded accelerograms at near-field seismic stations during the 2016–2017 Central Italy seismic sequence have been compared with synthetic accelerograms calculated by an extended finite-fault ground-motion simulation algorithm code. The outcomes show that synthetic seismograms can reproduce the high-frequency content of seismic waves at near-field areas. Then, in urbanized near-field areas, synthetic accelerograms can be fruitfully used in microzonation studies.

Kappa (κ) in the 2011 Great East Japan Earthquake

2020 ◽  
Vol 14 (06) ◽  
pp. 2050024
Author(s):  
Zhengru Tao ◽  
Xinyan Wang ◽  
Baihui Zhu ◽  
Tao Shang
Keyword(s):  
High Frequency ◽  
Site Response ◽  
Epicentral Distance ◽  
Soft Soil ◽  
Statistical Significance ◽  
Great East Japan Earthquake ◽  
Propagation Path ◽  
Data Sets ◽  
Borehole Data ◽  
Nonlinear Site Response

Kappa ([Formula: see text]) describes the amplitude decay of acceleration Fourier spectrum at high frequencies. Using the records of K-NET and KiK-net stations during the mainshock of the 2011 Great East Japan Earthquake, we examine if the typical measurement method of [Formula: see text] can be extended to this size of event and how propagation path and site condition affect [Formula: see text]. The strength of the linear relationship between epicentral distance and [Formula: see text] is the most apparent in the KiK-net borehole data; for other data sets, the statistical significance of the best-fitting logarithmic model is more tenuous. Our study on site effects reveals that high-frequency amplitudes diminish about 20% at soft soil stations than they do at hard rock stations. The effect on high-frequency filters is around diminution in most cases. And, the effect of nonlinear site response on [Formula: see text] values can be observed.

scholarly journals A Reappraisal of the Lurøy, Norway, Earthquake of 31 August 1819

2020 ◽  
Vol 91 (5) ◽  
pp. 2462-2472 ◽  
Author(s):  
Päivi B. Mäntyniemi ◽  
Mathilde B. Sørensen ◽  
Tatiana N. Tatevossian ◽  
Ruben E. Tatevossian ◽  
Björn Lund
Keyword(s):  
Historical Seismicity ◽  
Macroseismic Intensity ◽  
Macroseismic Data ◽  
Sources Of Information ◽  
Royal Swedish Academy ◽  
Intensity Assessment ◽  
Adequate Information ◽  
Data Points ◽  
Academy Of Sciences ◽  
Written Sources

Abstract Archives and libraries were visited to find previously unknown documents testifying to the Lurøy, Norway, earthquake of 31 August 1819 in northernmost continental Europe. The focus here is on Sweden, Finland, and Russia, which are important for determining the area of perceptibility east of Norway. The new written sources include 12 notes or entries in original archived documents, six contemporary newspaper reports, and two recollections written down years later. The original documentation uncovered is contributory to establishing the authenticity of the observations in Finland and Sweden. The dates of the original documentation allow tracing of the dissemination of eyewitness accounts in writing from the inner area of perceptibility southward to the larger documentation and population centers. New sources of information include weather reports of the Royal Swedish Academy of Sciences, minutes of its meetings, and correspondence sent to the Senate in Finland. The minutes of meetings of the Academy indicate that ample data were collected in the Swedish province of Västerbotten. We found no original Russian documentation but uncovered national newspapers that are more reliable than the previously used Parisian newspaper. To increase transparency, we provide the first list of macroseismic data points (MDPs) including the respective documentation that testify to the Lurøy earthquake. A macroseismic intensity was assigned to a locality, using the European Macroseismic Scale of 1998, when adequate information was available. Accounting for the uncertainty of intensity assessment, the magnitude was estimated as moment magnitude M=5.9±0.2, reconfirming the ranking as the largest onshore or nearshore earthquake in the historical seismicity record of Fennoscandia. In addition to the reappraisal of the 31 August 1819 earthquake, a macroseismic map is provided for the earthquake of 17 February 1819, which was felt in northern Finland and Sweden. Some of its MDPs were previously associated with the Lurøy earthquake.

scholarly journals Testing and Developing the Macroseismic Intensity Attenuation Relationships for the Vrancea (Romania) Crustal Earthquakes

2019 ◽  
Vol 362 ◽  
pp. 012058
Author(s):  
Constantin Angela Petruta ◽  
Moldovan Iren-Adelina ◽  
Partheniu Raluca ◽  
Manea Elena Florinela ◽  
Ionescu Constantin
Keyword(s):  
Macroseismic Intensity ◽  
Intensity Attenuation ◽  
Attenuation Relationships ◽  
Crustal Earthquakes

scholarly journals The correlations between optical variability and physical parameters of quasars in SDSS Stripe 82

2012 ◽  
Vol 8 (S290) ◽  
pp. 373-374
Author(s):  
Wenwen Zuo ◽  
Xue-Bing Wu ◽  
Yi-Qing Liu ◽  
Cheng-Liang Jiao
Keyword(s):  
Black Hole ◽  
Rest Frame ◽  
Accretion Rate ◽  
Physical Parameters ◽  
Optical Variability ◽  
Black Hole Mass ◽  
Disk Model ◽  
Bolometric Luminosity ◽  
Data Points ◽  
Quasar Variability

AbstractWe investigate the optical variability of 7658 quasars from SDSS Stripe 82. Taking advantage of a larger sample and relatively more data points for each quasar, we estimate variability amplitudes and divide the sample into small bins of redshift, rest-frame wavelength, black hole mass, Eddington ratio, and bolometric luminosity, respectively, to investigate the relationships between variability and these parameters. An anti-correlation between variability and rest-frame wavelength is found. The variability amplitude of radio-quiet quasars shows almost no cosmological evolution, but that of radio-loud ones may weakly anti-correlate with redshift. In addition, variability increases as either luminosity or Eddington ratio decreases. However, the relationship between variability and black hole mass is uncertain; it is negative when the influence of Eddington ratio is excluded, but positive when the influence of luminosity is excluded. The intrinsic distribution of variability amplitudes for radio-loud and radio-quiet quasars are different. Both radio-loud and radio-quiet quasars exhibit a bluer-when-brighter chromatism. Assuming that quasar variability is caused by variations of accretion rate, the Shakura–Sunyaev disk model can reproduce the tendencies of observed correlations between variability and rest-frame wavelength, luminosity as well as Eddington ratio, supporting that changes of accretion rate play an important role in producing the observed optical variability. However, the predicted positive correlation between variability and black hole mass seems to be inconsistent with the observed negative correlation between them in small bins of Eddington ratio, which suggests that other physical mechanisms may still need to be considered in modifying the simple accretion disk model.

Conditions for extreme wave runup on a vertical barrier by nonlinear dispersion

2014 ◽  
Vol 748 ◽  
pp. 768-788 ◽  
Author(s):  
Claudio Viotti ◽  
Francesco Carbone ◽  
Frédéric Dias
Keyword(s):  
Large Scale ◽  
Vertical Wall ◽  
Propagation Path ◽  
Physical Parameters ◽  
Propagation Time ◽  
Mathematical Framework ◽  
Wave Runup ◽  
Fully Nonlinear ◽  
Strongly Nonlinear ◽  
Nonlinear Modulation

AbstractThe runup of long strongly nonlinear waves impinging on a vertical wall can exceed six times the far-field amplitude of the incoming waves. This outcome stems from a precursory evolution process in which the wave height undergoes strong amplification due to the combined action of nonlinear steepening and dispersion, resulting in the formation of nonlinearly dispersive wave trains, i.e. undular bores. This part of the problem is first analysed separately, with emphasis on the wave amplitude growth rate during the development of undular bores within an evolving large-scale background. The growth of the largest wave in the group is seen to reflect the asymptotic time scaling provided by nonlinear modulation theory rather closely, even in the case of fully nonlinear evolution and moderately slow modulations. In order to address the effect of such a dynamics on the subsequent wall runup, numerical simulations of evolving long-wave groups are then carried out in a computational wave tank delimited by vertical walls. Conditions for optimal runup efficiency are sought with respect to the main physical parameters characterizing the incident waves, namely the wavelength, the length of the propagation path and the initial amplitude. Extreme runup is found to be strongly correlated to the ratio between the available propagation time and the shallow-water nonlinear time scale. The problem is studied in the twofold mathematical framework of the fully nonlinear free-surface Euler equations and the strongly nonlinear Serre–Green–Naghdi model. The performance of the reduced model in providing accurate long-time predictions can therefore be assessed.

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