scholarly journals GROUND MOTION PREDICTION AT THE DAM SITES IN SW ROMANIA FOR MODERATE VRANCEA SUBCRUSTAL EARTHQUAKES

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Anica Otilia Placinta ◽  
Emilia Popescu ◽  
Iren-Adelina Moldovan ◽  
Mircea Radulian ◽  
Andrei Mihai
Keyword(s):  
Seismic Hazard ◽  
Seismic Waves ◽  
Physical Parameters ◽  
Attenuation Relations ◽  
Local Conditions ◽  
National Network ◽  
Soil Movement ◽  
Attenuation Relationships ◽  
South West ◽  
Subcrustal Earthquakes

The seismic hazard studies of the last 30 years have been largely carried out taking into account the needs of the construction engineers, by linking the specific quantities of soil movement with the physical parameters determined instrumentally, namely, with the maximum values of soil acceleration. At present, interest in the results of hazard studies has increased and has extended to other areas such as insurance or design companies, environmental protection, etc. A fundamental element in the estimation of seismic hazard is the variation of the amplitude of the movement of the soil according to the distance, magnitude and local conditions. To understand and prevent the effects of the strong Vrancea earthquakes in the dam sites located in the South West of Romania, we study the seismic waves attenuation relations using the accelerations recorded by the national network of K2 accelerometers, following the moderate Vrancea intermediate earthquakes. The study area includes the largest agglomeration of dams in Romania, with almost 100 dams out of the 250 large dams. One of the most important specific requirements towards dams' safety is the seismic risk and hazard assessment and the computation of attenuation relationships is one of the most important steps of the work. The main objective of the present work is the evaluation of the specific attenuation relationships of the seismic wave propagating from Vrancea subcrustal focus toward south-west, with direct application for the dams situated in the area.

Numerical simulation of seismic waves in porous media components

2021 ◽  
Vol 9 (1) ◽  
pp. 4-30
Author(s):  
M. Azeredo ◽  
◽  
V. Priimenko ◽  
Keyword(s):  
Numerical Simulation ◽  
Porous Medium ◽  
High Frequency ◽  
Seismic Waves ◽  
Computational Algorithm ◽  
Low Frequency ◽  
Physical Parameters ◽  
Mathematical Algorithm ◽  
Biot Equations ◽  
Attenuation And Dispersion

This work presents a mathematical algorithm for modeling the propagation of poroelastic waves. We have shown how the classical Biot equations can be put into Ursin’s form in a plane-layered 3D porous medium. Using this form, we have derived explicit for- mulas that can be used as the basis of an efficient computational algorithm. To validate the algorithm, numerical simulations were performed using both the poroelastic and equivalent elastic models. The results obtained confirmed the proposed algorithm’s reliability, identify- ing the main wave events in both low-frequency and high-frequency regimes in the reservoir and laboratory scales, respectively. We have also illustrated the influence of some physical parameters on the attenuation and dispersion of the slow wave.

scholarly journals A hybrid model for mapping simplified seismic response via a GIS-metamodel approach

2014 ◽  
Vol 14 (7) ◽  
pp. 1703-1718 ◽  
Author(s):  
G. Grelle ◽  
L. Bonito ◽  
P. Revellino ◽  
L. Guerriero ◽  
F. M. Guadagno
Keyword(s):  
Seismic Hazard ◽  
Seismic Response ◽  
Hybrid Model ◽  
Computational Models ◽  
Site Response ◽  
Seismic Hazard Assessment ◽  
Physical Parameters ◽  
Seismic Zone ◽  
Acceleration Response ◽  
Good Correspondence

Abstract. In earthquake-prone areas, site seismic response due to lithostratigraphic sequence plays a key role in seismic hazard assessment. A hybrid model, consisting of GIS and metamodel (model of model) procedures, was introduced aimed at estimating the 1-D spatial seismic site response in accordance with spatial variability of sediment parameters. Inputs and outputs are provided and processed by means of an appropriate GIS model, named GIS Cubic Model (GCM). This consists of a block-layered parametric structure aimed at resolving a predicted metamodel by means of pixel to pixel vertical computing. The metamodel, opportunely calibrated, is able to emulate the classic shape of the spectral acceleration response in relation to the main physical parameters that characterize the spectrum itself. Therefore, via the GCM structure and the metamodel, the hybrid model provides maps of normalized acceleration response spectra. The hybrid model was applied and tested on the built-up area of the San Giorgio del Sannio village, located in a high-risk seismic zone of southern Italy. Efficiency tests showed a good correspondence between the spectral values resulting from the proposed approach and the 1-D physical computational models. Supported by lithology and geophysical data and corresponding accurate interpretation regarding modelling, the hybrid model can be an efficient tool in assessing urban planning seismic hazard/risk.

A Monte Carlo approach to seismic hazard analysis

1999 ◽  
Vol 89 (4) ◽  
pp. 854-866 ◽  
Author(s):  
John E. Ebel ◽  
Alan L. Kafka
Keyword(s):  
Monte Carlo ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Epicentral Distance ◽  
Ground Motions ◽  
Source Parameters ◽  
Parametric Models ◽  
Earthquake Catalog ◽  
Attenuation Relations ◽  
Ground Motion Attenuation

Abstract We have developed a Monte Carlo methodology for the estimation of seismic hazard at a site or across an area. This method uses a multitudinous resampling of an earthquake catalog, perhaps supplemented by parametric models, to construct synthetic earthquake catalogs and then to find earthquake ground motions from which the hazard values are found. Large earthquakes extrapolated from a Gutenberg-Richter recurrence relation and characteristic earthquakes can be included in the analysis. For the ground motion attenuation with distance, the method can use either a set of observed ground motion observations from which estimates are randomly selected, a table of ground motion values as a function of epicentral distance and magnitude, or a parametric ground motion attenuation relation. The method has been tested for sites in New England using an earthquake catalog for the northeastern United States and southeastern Canada, and it yields reasonable ground motions at standard seismic hazard values. This is true both when published ground motion attenuation relations and when a dataset of observed peak acceleration observations are used to compute the ground motion attenuation with distance. The hazard values depend to some extent on the duration of the synthetic catalog and the specific ground motion attenuation used, and the uncertainty in the ground motions increases with decreasing hazard probability. The program gives peak accelerations that are comparable to those of the 1996 U.S. national seismic hazard maps. The method can be adapted to compute seismic hazard for cases where there are temporal or spatial variations in earthquake occurrence rates or source parameters.

scholarly journals Determination of Local Site-Specific Spectra Using Probabilistic Seismic Hazard Analysis for Bitlis Province, Turkey

2015 ◽  
Vol 19 (2) ◽  
pp. 129-134 ◽  
Author(s):  
Ercan Işık ◽  
Mustafa Kutanis
Keyword(s):  
Seismic Hazard ◽  
Hazard Analysis ◽  
Seismic Hazard Assessment ◽  
Seismic Source ◽  
Response Spectra ◽  
Probabilistic Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard ◽  
Source Characterization ◽  
Site Specific ◽  
Attenuation Relationships

<p>In this study, site-specific earthquake spectra for Bitlis province in Lake Van Basin has been obtained. It is noteworthy that, in probabilistic seismic hazard assessment, as a first stage data from geological studies and records from the instrumental period were compiled to make a seismic source characterization for the study region.The probabilistic seismic hazard curves for Bitlis were developed based on selected appropriate attenuation relationships, at rock sites, with a probability of exceedance 2%, 10% and 50% in 50 year periods. The obtained results were compared with the spectral responses proposed for seismic evaluation and retrofit of the building structure in Turkish Earthquake Code, Section 2. At the end of this study, it is apprehended that the Code proposed earthquake response spectra are not sufficient for the performance evaluation of the existing structures and the current estimations show that the potential seismic hazard research of the Turkey is underestimated in the code.Therefore, site- specific design spectra for the region should be developed, which reflect the characteristics of local sites.</p><p> </p><p><strong>Determinación de espectros de sitio específico locales a través del análisis probabilístico de amenazas sísmicaspara la provincia de Bitlis, Turquía</strong></p><p> </p><p><strong>Resumen</strong></p>En este estudio se obtuvieron espectros de terremoto de sitio específico para la cuenca del Lago de Van, en la provincia de Bitlis, al este de Turquía. La primera fase del trabajo consistió en una evaluación probabilística de riesgo sísmico donde se compilaron los estudios geológicos y registros del período instrumental para hacer una caracterización de fuente sísmica en la región de estudio. Las curvas de amenaza sísmica para la provincia de Bitlis se desarrollaron con base en las relaciones de atenuación apropiada seleccionadas en los sitios rocosos, con una probabilidad de exceso de 2 %, 10 % y 50 % durante 50 años. Los resultados obtenidos se compararon con las respuestas de espectro propuestas para la evaluación sísmica y modernización de estructuras contempladas en el Código de Terremoto de Turquía, en la sección 2. En la parte final de este trabajo se comprende que las respuestas de espectros de terremoto propuestos en el código no son suficientes para la evaluación de desempeño de las estructuras existentes y que las estimaciones actuales muestran que la investigación de amenazas potenciales sísmicas en Turquía está subestimada en el código. Por lo tanto, el diseño de espectros de sitio específico para la región se debe desarrollar, ya que permitiría conocer las singularidades locales.</p>

scholarly journals Path and site effects deduced from transfrontier internet macroseismic data of two recent M4 earthquakes in NW Europe

2016 ◽  
Author(s):  
Koen Van Noten ◽  
Thomas Lecocq ◽  
Christophe Sira ◽  
Klaus-G. Hinzen ◽  
Thierry Camelbeeck
Keyword(s):  
Seismic Waves ◽  
Sedimentary Cover ◽  
Grid Cell ◽  
Individual Response ◽  
Macroseismic Data ◽  
Grid Cells ◽  
Attenuation Relations ◽  
Circular Distribution ◽  
Intensity Attenuation ◽  
Zip Code

Abstract. The online collection of earthquake testimonies in Europe is strongly fragmented across numerous seismological agencies. This paper demonstrates how collecting and merging “Did You Feel It?” (DYFI) institutional macroseismic data strongly improves the quality of real-time intensity maps. Instead of using ZIP code Community Internet Intensity Maps we geocode individual response addresses for location improvement, assign intensities to grouped answers within 100 km2 grid cells, and generate intensity attenuation relations from the grid cell intensities. Grid cell intensity maps are less subjective and illustrate a more homogeneous intensity distribution than the ZIP code intensity maps. Using grid cells for ground motion analysis offers an advanced method for exchanging transfrontier equal-area intensity data without sharing any personal’s information. The applicability of the method is demonstrated on the DYFI responses of two well-felt earthquakes: the 8 September 2011 ML 4.3 (MW 3.7) Goch (Germany) and the 22 May 2015 ML 4.2 (MW 3.7) Ramsgate (UK) earthquakes. Both events resulted in non-circular distribution of intensities which is not explained by geometrical amplitude attenuation alone but illustrates an important low-pass filtering due the sedimentary cover above the Anglo-Brabant Massif and in the Lower Rhine Graben. Our study illustrates the effect of increasing bedrock depth on intensity attenuation and the importance of the WNW-ESE Caledonian structural axis of the Anglo-Brabant Massif on seismic wave propagation: seismic waves are less attenuated – high Q – along the strike of the massif but are stronger attenuated – low Q – perpendicular to this structure, especially when they cross rheologically different seismotectonic units that are separated by crustal-rooted faults.

The 1904 Ms6.8 Mw7.0-7.2 Cape Turnagain, New Zealand, earthquake

2006 ◽  
Vol 39 (4) ◽  
pp. 183-207
Author(s):  
G. L. Downes
Keyword(s):  
New Zealand ◽  
Surface Wave ◽  
Seismic Hazard ◽  
Goodness Of Fit ◽  
Central Business District ◽  
Maximum Magnitude ◽  
Surface Wave Magnitude ◽  
Plate Interface ◽  
Attenuation Relations ◽  
Instrumental Records

The 1904 August 09 NZT (August 08 UT) MS6.8 earthquake caused widespread structural and chimney damage from Napier to Wellington and was felt over a large part of New Zealand. Other than a brief paper in 1905, and determinations of its surface wave magnitude in the last 20 years, little has been done to better locate the earthquake or detail its effects. Comprehensive data have now been obtained from searches of historical documents, including newspapers, private and government papers, as well as instrumental records. Interpretation of the intensity data shows that the earthquake was probably centred near Cape Turnagain at relatively shallow depth. The paucity of aftershocks suggests that the earthquake occurred either on the subduction interface, or in the lower seismicity band or upper mantle of the subducting Pacific Plate. The area encompassed by the higher intensity isoseismals suggests the earthquake had a magnitude greater than the calculated surface wave magnitude MS6.75 ± 0.14 — possibly as high as MW7.2. At this magnitude, the earthquake becomes a more significant event in New Zealand’s historical record, and certainly the largest earthquake suspected of rupturing the plate interface along the Hikurangi Margin. A notable feature of the earthquake is the chimney and parapet damage caused in parts of Wellington Central Business District, approximately 170 km from the epicentre. Much of the city and inner suburbs experienced MM5-6, while MM6-7 occurred in several areas, mostly in those areas that are recognised as possibly susceptible to shaking enhancement, but also in several locations outside these areas. The 1904 Cape Turnagain earthquake has several implications for seismic hazard dependent on whether it was intra-slab or on the plate interface. Of particular importance, are the questions whether the damage in Wellington is exceptional and could represent microzone, focussing or directivity effects; the goodness of fit of the intensity distribution to modelled isoseismals using published attenuation relations; the compatibility of the magnitude with the maximum magnitude/magnitude cut-offs used in this area in the New Zealand Probabilistic Seismic Hazard model; and finally, the possibility that the 1904 earthquake might characterise plate interface earthquakes in southern Hawke’s Bay.

scholarly journals Uncertainties in attenuation relations for New Zealand seismic hazard analysis

1986 ◽  
Vol 19 (1) ◽  
pp. 28-39 ◽  
Author(s):  
G. H. McVerry
Keyword(s):  
New Zealand ◽  
Seismic Hazard ◽  
Hazard Analysis ◽  
Response Spectrum ◽  
Strong Motion ◽  
Seismic Hazard Analysis ◽  
Ground Acceleration ◽  
Attenuation Relations ◽  
Ground Shaking ◽  
Acceleration Data

Probabilistic techniques for seismic hazard analysis have
come into vogue in New Zealand for both the assessment of major projects and the development and review of seismic design codes. However, there are considerable uncertainties in the modelling
 of the strong-motion attenuation, which is necessarily based largely on overseas data. An excellent agreement is obtained between an average 5% damped response spectrum for New Zealand alluvial sites in the 20 to 59 km distance range and 5.4 to 6.0 magnitude class and that given by a Japanese model. Unfortunately, this corresponds to only about half the amplitude levels of 150 year spectra relevant to code design. The much more rapid decay
of ground shaking with distance in New Zealand has led to a considerable modification based on maximum ground acceleration
data from the Inangahua earthquake of the distance-dependence
of the Japanese response spectra model. Less scatter in New Zealand data has resulted in adopting a lower standard deviation for the attenuation model, which is important in reducing the considerable "probabilistic enhancement" of the hazard estimates. Regional differences in attenuation shown by intensities are difficult to resolve from the strong-motion acceleration data, apart from lower accelerations in Fiordland.

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