scholarly journals Estimation of near-surface attenuation in the tectonically complex contact area of the Northwestern External Dinarides and the Adriatic foreland

2019 ◽  
Author(s):  
Snježana Markušić ◽  
Davor Stanko ◽  
Tvrtko Korbar ◽  
Ivica Sović
Keyword(s):  
Amplitude Spectrum ◽  
Seismic Source ◽  
Propagation Path ◽  
Site Conditions ◽  
Coda Q ◽  
Near Surface ◽  
Contour Lines ◽  
Geological Features ◽  
A Site ◽  
External Dinarides

Abstract. Seismic-induced ground motion at a site is generally influenced by seismic source, propagation path and local site conditions. Over the last several decades, researchers have consistently asserted that for near site attenuation, the spectral parameter kappa is subject primarily to site conditions. In this research we estimated parameter kappa based on the acceleration amplitude spectrum of shear waves, from the selected recordings of local earthquakes from seismological stations situated in the western part of Croatia from the slope of the high-frequency part. The spatial distribution of individual kappa values is compared with the azimuthal distribution of earthquake epicentres, with Vs30 values and the published coda-Q values for each station, as well as with isoseismal maps for several stronger events in the investigated area, along with the geological features. The dextral shift of crustal segments and frontal thrust of the External Dinarides along the Kvarner fault zone has probably had an impact on the geometry of the kappa parameter contour lines. These results are important for gaining further insight into the attenuation of near-surface crust layers in the Northwestern External Dinarides and the associated Adriatic foreland, as well as in similar geotectonic settings.

scholarly journals Estimation of near-surface attenuation in the tectonically complex contact area of the northwestern External Dinarides and the Adriatic foreland

2019 ◽  
Vol 19 (12) ◽  
pp. 2701-2714 ◽  
Author(s):  
Snježana Markušić ◽  
Davor Stanko ◽  
Tvrtko Korbar ◽  
Ivica Sović
Keyword(s):  
Wave Attenuation ◽  
Amplitude Spectrum ◽  
Seismic Source ◽  
Field Trapping ◽  
Fault Zones ◽  
Propagation Path ◽  
Site Conditions ◽  
Coda Q ◽  
Near Surface ◽  
External Dinarides

Abstract. Seismically induced ground motion at a site is generally influenced by the seismic source, the propagation path and the local site conditions. Over the last several decades, researchers have consistently asserted that for near-site attenuation, the spectral parameter κ is subject primarily to the site conditions. In this research, we estimated the parameter κ based on the acceleration amplitude spectrum of shear waves from local earthquakes recorded by seismological stations situated in the western part of Croatia from the slope of the high-frequency part. The spatial distribution of κ values is comparable with seismological, geophysical and geological features, with the published coda-Q values for each station as well as with the isoseismal maps for selected stronger earthquakes in the study area. The complex pattern of longitudinal and transversal major late-orogenic fault zones dissecting early-orogenic thin-skinned tectonic cover in the Kvarner area and the shallow depth to the Moho (Mohorovičić discontinuity) in the Adriatic foreland (southern Istria) are probably responsible for a significant part of wave attenuation and for the anisotropy of attenuation. Regional near-surface attenuation distribution and modelled macroseismic fields point to the conclusion that attenuation properties of rocks in the northwestern External Dinarides are far from isotropic, and the most likely anisotropy sources are the preferential orientations of cracks and fractures under the local tectonic stress field, trapping of waves along major faults (waveguides), and/or attenuation within the fault zones. These results are important for gaining further insight into the attenuation of near-surface crust layers in the northwestern External Dinarides and the associated Adriatic foreland as well as in similar geotectonic settings.

scholarly journals Field comparison of shallow P‐wave seismic sources near Houston, Texas

Geophysics ◽  
1994 ◽  
Vol 59 (11) ◽  
pp. 1713-1728 ◽  
Author(s):  
Richard D. Miller ◽  
Susan E. Pullan ◽  
Don W. Steeples ◽  
James A. Hunter
Keyword(s):  
Water Table ◽  
Seismic Source ◽  
Dominant Frequency ◽  
P Wave ◽  
Near Surface ◽  
Site Characteristics ◽  
Water Well ◽  
Local Water ◽  
A Site ◽  
Different Sources

A shallow P‐wave seismic source comparison was conducted at a site near Houston, Texas where the depth to the water table was approximately 7 m, and near‐surface materials consisted of clays, sands, and gravels. Data from twelve different sources during this November 1991 comparison are displayed and analyzed. Reflection events are interpretable at about 40 ms on some 220-Hz analog low‐cut filtered field files, and at 60 ms on most 110‐ and 220-Hz analog low‐cut filtered field files. Calculations and local water well information suggest the 40-ms event is from the top of the water table. Subsurface explosive sources seem to possess the highest dominant frequency, broadest bandwidth, and recorded amplitudes and, therefore, have the greatest resolution potential at this site. Our previous work and that of our colleagues suggests that, given a specific set of site characteristics, any source could dominate the comparison categories addressed here.

scholarly journals Technical Note: Novel method for water vapour monitoring using wireless communication networks measurements

2009 ◽  
Vol 9 (7) ◽  
pp. 2413-2418 ◽  
Author(s):  
N. David ◽  
P. Alpert ◽  
H. Messer
Keyword(s):  
Wireless Communication ◽  
Water Vapour ◽  
Communication Networks ◽  
Weather Conditions ◽  
Technical Note ◽  
Base Stations ◽  
Propagation Path ◽  
High Temporal Resolution ◽  
Wireless Communication Networks ◽  
Near Surface

Abstract. We propose a new technique that overcomes the obstacles of the existing methods for monitoring near-surface water vapour, by estimating humidity from data collected through existing wireless communication networks. Weather conditions and atmospheric phenomena affect the electromagnetic channel, causing attenuations to the radio signals. Thus, wireless communication networks are in effect built-in environmental monitoring facilities. The wireless microwave links, used in these networks, are widely deployed by cellular providers for backhaul communication between base stations, a few tens of meters above ground level. As a result, if all available measurements are used, the proposed method can provide moisture observations with high spatial resolution and potentially high temporal resolution. Further, the implementation cost is minimal, since the data used are already collected and saved by the cellular operators. In addition – many of these links are installed in areas where access is difficult such as orographic terrain and complex topography. As such, our method enables measurements in places that have been hard to measure in the past, or have never been measured before. The technique is restricted to weather conditions which exclude rain, fog or clouds along the propagation path. Strong winds that may cause movement of the link transmitter or receiver (or both) may also interfere with the ability to conduct accurate measurements. We present results from real-data measurements taken from two microwave links used in a backhaul cellular network that show convincing correlation to surface station humidity measurements. The measurements were taken daily in two sites, one in northern Israel (28 measurements), the other in central Israel (29 measurements). The correlation between the microwave link measurements and the humidity gauges were 0.9 and 0.82 for the north and central sites, respectively. The Root Mean Square Differences (RMSD) were 1.8 g/m3 and 3.4 g/m3 for the northern and central site measurements, respectively.

scholarly journals Environmental monitoring of soil pollution in urban areas (a case study from Heraklion city, Central Crete, Greece)

2017 ◽  
Vol 47 (2) ◽  
pp. 963
Author(s):  
E. Kokinou ◽  
C. Belonaki ◽  
D. Sakadakis ◽  
K. Sakadaki
Keyword(s):  
Magnetic Susceptibility ◽  
Urban Areas ◽  
Magnetic Measurements ◽  
Topographic Map ◽  
Near Surface ◽  
Thermomagnetic Analysis ◽  
Geological Features ◽  
Digital Elevation ◽  
Elevation Model

Main scope of the present study is to combine topographic and geological data, magnetic susceptibility and thermomagnetic analysis in order to investigate the magnetic properties of the near surface soils in possible polluted urban areas. For this purpose, a power plant with a dense traffic net around it, located in the NW section of Heraklion city in Crete was selected to be the study area. Surface soil samples have been collected from the area under investigation and they were analyzed in order to estimate the spatial distribution of the magnetic susceptibility. Loci of high values of the magnetic susceptibility within the study area gave rise to further proceed to thermomagnetic analysis of the selected samples. GIS techniques were used for mapping the magnetic measurements on the various topographic and geological features of the area. The digital elevation model was created by the digitization of the topographic map contours (1:5000 scale maps). The combination of the above techniques indicate high values of the magnetic susceptibility especially in the northeastern part of the investigated area, possibly related to pollution due to the presence of heavy metals.

Subsurface Investigation

2015 ◽  
pp. 744-795
Keyword(s):  
Field Tests ◽  
Field Investigation ◽  
Soil Parameters ◽  
Near Surface ◽  
Ground Investigation ◽  
Geophysical Techniques ◽  
Vertical Profiling ◽  
Sample Recovery ◽  
Subsurface Investigation ◽  
A Site

A good knowledge about a site including its subsurface conditions is very important in its safe and economical development. It is therefore an essential preliminary to the construction of any civil engineering work. This chapter outlines the objectives of site characterization and the general objectives of geotechnical investigation. It discusses the phases of field investigation and the stages of a full exploratory program including methods of sample recovery and field tests and sampling methods. Geophysical techniques can contribute very greatly to the process of ground investigation by allowing an assessment, in qualitative terms, of the lateral variability and vertical profiling of the near-surface materials beneath a site. Some of these geophysical techniques are discussed in the chapter. Laboratory examination/verification and testing should be made of representative portions of the samples to establish appropriate soil parameters. Some soil parameters may be estimated by correlations. The results of the subsurface investigation and related testing, together with interpretations, discussions, and foundation recommendations, are usually presented in the form of a detailed soil report.

A Stochastic Semi-Physical Model of Seismic Ground Motions in Time Domain

2018 ◽  
Vol 12 (03) ◽  
pp. 1850006 ◽  
Author(s):  
Yanqiong Ding ◽  
Yongbo Peng ◽  
Jie Li
Keyword(s):  
Probability Density ◽  
Ground Motions ◽  
Seismic Source ◽  
Response Spectra ◽  
Propagation Path ◽  
Superposition Method ◽  
Probability Density Evolution Method ◽  
Proposed Model ◽  
Time Histories ◽  
Seismic Accelerations

A stochastic function model of seismic ground motions is presented in this paper. It is derived from the consideration of physical mechanisms of seismic ground motions. The model includes the randomness inherent in the seismic source, propagation path and local site. For logical selection of the seismic acceleration records, a cluster analysis method is employed. Statistical distributions of the random parameters associated with the proposed model are identified using the selected data. Superposition method of narrow-band wave groups is then adopted to simulate non-stationary seismic ground motions. In order to verify the feasibility of the proposed model, comparative studies of time histories and response spectra of the simulated seismic accelerations against those of the recorded seismic accelerations are carried out. Their probability density functions, moreover, are readily investigated by virtue of the probability density evolution method.

Geoheritage values of one of the largest maar craters in the Arabian Peninsula: the Al Wahbah Crater and other volcanoes (Harrat Kishb, Saudi Arabia)

2013 ◽  
Vol 5 (2) ◽  
Author(s):  
Mohammed Moufti ◽  
Károly Németh ◽  
Nabil El-Masry ◽  
Atef Qaddah
Keyword(s):  
Saudi Arabia ◽  
Lava Flow ◽  
Arabian Peninsula ◽  
Volcanic Hazards ◽  
Scoria Cone ◽  
Volcanic Field ◽  
Flow Surface ◽  
Geological Features ◽  
A Site ◽  
Tephra Ring

AbstractAl Wahbah Crater is one of the largest and deepest Quaternary maar craters in the Arabian Peninsula. It is NW-SE-elongated, ∼2.3 km wide, ∼250 m deep and surrounded by an irregular near-perpendicular crater wall cut deeply into the Proterozoic diorite basement. Very few scientific studies have been conducted on this unique site, especially in respect to understanding the associated volcanic eruption processes. Al Wahbah and adjacent large explosion craters are currently a research subject in an international project, Volcanic Risk in Saudi Arabia (VORiSA). The focus of VORiSA is to characterise the volcanic hazards and eruption mechanisms of the vast volcanic fields in Western Saudi Arabia, while also defining the unique volcanic features of this region for use in future geoconservation, geoeducation and geotourism projects. Al Wahbah is inferred to be a maar crater that formed due to an explosive interaction of magma and water. The crater is surrounded by a tephra ring that consists predominantly of base surge deposits accumulated over a pre-maar scoria cone and underlying multiple lava flow units. The tephra ring acted as an obstacle against younger lava flows that were diverted along the margin of the tephra ring creating unique lava flow surface textures that recorded inflation and deflation processes along the margin of the post-maar lava flow. Al Wahbah is a unique geological feature that is not only a dramatic landform but also a site that can promote our understanding of complex phreatomagmatic monogenetic volcanism. The complex geological features perfectly preserved at Al Wahbah makes this site as an excellent geotope and a potential centre of geoeducation programs that could lead to the establishment of a geopark in the broader area at the Kishb Volcanic Field.

Seismoelectric imaging of shallow targets

Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. G9-G20 ◽  
Author(s):  
Seth S. Haines ◽  
Steven R. Pride ◽  
Simon L. Klemperer ◽  
Biondo Biondi
Keyword(s):  
Electric Fields ◽  
Field Experiments ◽  
Electrode Array ◽  
Seismic Source ◽  
Analytical Models ◽  
Synthetic Image ◽  
Response Signal ◽  
Line Geometry ◽  
Near Surface ◽  
Promising Application

We have undertaken a series of controlled field experiments to develop seismoelectric experimental methods for near-surface applications and to improve our understanding of seismoelectric phenomena. In a set of off-line geometry surveys (source separated from the receiver line), we place seismic sources and electrode array receivers on opposite sides of a man-made target (two sand-filled trenches) to record separately two previously documented seismoelectric modes: (1) the electromagnetic interface response signal created at the target and (2) the coseismic electric fields located within a compressional seismic wave. With the seismic source point in the center of a linear electrode array, we identify the previously undocumented seismoelectric direct field, and the Lorentz field of the metal hammer plate moving in the earth’s magnetic field. We place the seismic source in the center of a circular array of electrodes (radial and circumferential orientations) to analyze the source-related direct and Lorentz fields and to establish that these fields can be understood in terms of simple analytical models. Using an off-line geometry, we create a multifold, 2D image of our trenches as dipping layers, and we also produce a complementary synthetic image through numerical modeling. These images demonstrate that off-line geometry (e.g., crosswell) surveys offer a particularly promising application of the seismoelectric method because they effectively separate the interface response signal from the (generally much stronger) coseismic and source-related fields.

scholarly journals Specificity of the seismic material obtained in complex seismo geological conditions (swamp zone)

2019 ◽  
Author(s):  
А.А. Левицкий ◽  
А.В. Рудаков ◽  
М.С. Левицкая
Keyword(s):  
Negative Impact ◽  
Seismic Source ◽  
Integrated Approach ◽  
Seismic Exploration ◽  
Near Surface ◽  
Factors Affecting ◽  
Geological Conditions ◽  
Seismic Recording ◽  
Surface Section

Основная цель работы – описание новых технических и методологических средств, используемых АО «Южморгеология» при проведении полевых сейсморазведочных работ МОГТ 3D в лиманно-плавневых зонах Славянского района Краснодарского края в 2014-2015 гг. Представлены основные результаты опытных работ, обоснован выбор параметров съемки и их влияние на качество сейсмической записи: заглубление пневмоисточников BOLT 2200LL-BHS, количество накоплений возбуждения и необходимая глубина погружения датчиков регистраторов. В качестве датчиков регистраторов использовались маршфоны «СВГ-6», которые задавливались с помощью металлического шеста с креплением на конце на глубину 1,0–2,5 м до достижения уверенного контакта с твердой поверхностью (плотный грунт, глинистая подошва), снижая негативное влияние шумов (микросейсм) от корневой системы камышей (рис. 2А, В). Группирование «СВГ-6» шестью последовательно соединенными геофонами (GS-20DX) увеличило чувствительность датчика к слабым сигналам, возбуждаемым, в слабо консолидированной толще, а его прочная конструкция и металлическая проушина, позволила извлекать маршфон из скважины, полностью заполненной водой и шламом.  Приведены основные свойства верхней части разреза (ВЧР) исследуемой площади по данным бурения с кратким описанием литологической характеристика разреза до глубины 10 м. Показаны сейсмограммы, полученные на одном участке в разных сейсмогеологических условиях. Выявлена зависимость распределения значений среднеквадратичных амплитуд и доминантных частот по площади от поверхностных условий возбуждения и приема колебаний. Данная зависимость также прослеживается на предварительных временных разрезах. Были проанализированы основные факторы, влияющие на качество получаемого сейсмического материала. На основе проведенного исследования авторами обосновывается необходимость использования комплексного подхода к анализу качества сейсмических данных при работах в сложных сейсмогеологических условиях. В качестве вывода приведены основные рекомендации к проведению сейсморазведочных работ в лиманно-плавневых зонах. The main objective of the work is the description of new technical and methodological tools used by Yuzhmorgeologiya JSC when conducting CDP 3D field seismic surveys in the estuaries of the Slavyansk district of the Krasnodar Region in 2014-2015. The main results of the experimental work are presented; the choice of survey parameters and their impact on the quality of the seismic recording is validated: digging-in of the seismic source points BOLT 2200LL-BHS, the number of excitation accumulations and the required depth of recorder sensors. Geophones “SVG-6” were used as sensors of the recorders, which were crushed with a metal pole with a fastening at the end to a depth of 1.0–2.5 m until steady contact with a solid surface (dense soil, clay base) was achieved, reducing the negative impact noise (microseism) from the root system of reeds (Fig. 2A, B). Grouping the SVG-6 with six consecutive geophones (GS-20DX) increased the sensitivity of the equipment to weak signals being excited in a weakly consolidated layer, and its robust design and metal eye, made it possible to extract the geophone from a well completely filled with water and sludge. The basic properties of the upper part of the section (near-surface section) of the studied area are given according to the drilling data with a brief description of the lithological characteristics of the section to a depth of 10 m. Seismograms obtained at one site in different seismic and geological conditions are shown. The dependence of the distribution of values of root-mean-square amplitudes and dominant frequencies over the area on the surface conditions of excitation and reception of vibrations is revealed. This dependence is also observed in the preliminary time sections. The main factors affecting the quality of the obtained seismic material were analyzed. Based on the present study, the authors validate the need for the use of an integrated approach to analyzing the quality of seismic data when working under complex seismic and geological conditions. As a conclusion, the main recommendations for seismic exploration in the estuaries are presented.

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