This document discusses the distribution of slip along earthquake faults based on analyses of five major earthquake slip models. It finds that the distribution follows a piecewise Gutenberg-Richter law, with different b-values above and below a transition point. For smaller slips, b is near 1, while for larger slips b is greater than 1. It analyzes the slip distributions using rank-ordering analysis to overcome data limitations. This verifies the existence of power laws with different scaling constants in the two slip regimes identified.
The document describes the SHARE European Earthquake Catalogue (SHEEC) which covers earthquakes from 1000-1899 in Europe. It was compiled using the historical earthquake dataset and background information from the NERIES project, which established a distributed archive of historical earthquake data and methodology for assessing earthquake parameters from macroseismic data points. Earthquake parameters were determined through processing macroseismic data points using updated, regionally calibrated procedures. A strategy focused on maximizing the homogeneity of epicentral location and magnitude across the catalog. The catalog provides location and magnitude uncertainties.
This document proposes a modification to the Gutenberg-Richter law to describe the cumulative distribution of earthquake magnitudes using concepts from nonextensive statistical mechanics. It introduces a new "q-stretched exponential" form for the modified Gutenberg-Richter law and fits this form to seismic data from California and Iran. The empirical data fits extremely well with the proposed modification over the entire range of magnitudes. Nonextensive statistical mechanics is applied to derive a q-exponential distribution for the surface size of fragments produced during earthquakes. A new hypothetical relationship is also proposed between the surface size of fragments and the released energy.
This document summarizes a study on the geothermal conditions of the Marmara Sea region in northwest Turkey. The researchers collected temperature data from 44 shallow water wells and 9 oil wells up to 2500m deep to determine surface heat flow density. They also measured thermal conductivities of rock samples. Temperature profiles in the shallow wells showed nonlinear increases with depth likely due to water movement. Repeated measurements over a year showed stable temperature distributions. Heat flow density varied regionally from 35 to 115 mW/m2, with a mean of 60 mW/m2. Higher values were found in areas of active extension south of the Marmara Sea. The spatial pattern of thermal springs did not coincide with heat flow patterns, as their appearance
This document discusses the distribution of slip along earthquake faults based on analyses of five major earthquake slip models. It finds that the distribution follows a piecewise Gutenberg-Richter law, with different b-values above and below a transition point. For smaller slips, b is near 1, while for larger slips b is greater than 1. It analyzes the slip distributions using rank-ordering analysis to overcome data limitations. This verifies the existence of power laws with different scaling constants in the two slip regimes identified.
The document describes the SHARE European Earthquake Catalogue (SHEEC) which covers earthquakes from 1000-1899 in Europe. It was compiled using the historical earthquake dataset and background information from the NERIES project, which established a distributed archive of historical earthquake data and methodology for assessing earthquake parameters from macroseismic data points. Earthquake parameters were determined through processing macroseismic data points using updated, regionally calibrated procedures. A strategy focused on maximizing the homogeneity of epicentral location and magnitude across the catalog. The catalog provides location and magnitude uncertainties.
This document proposes a modification to the Gutenberg-Richter law to describe the cumulative distribution of earthquake magnitudes using concepts from nonextensive statistical mechanics. It introduces a new "q-stretched exponential" form for the modified Gutenberg-Richter law and fits this form to seismic data from California and Iran. The empirical data fits extremely well with the proposed modification over the entire range of magnitudes. Nonextensive statistical mechanics is applied to derive a q-exponential distribution for the surface size of fragments produced during earthquakes. A new hypothetical relationship is also proposed between the surface size of fragments and the released energy.
This document summarizes a study on the geothermal conditions of the Marmara Sea region in northwest Turkey. The researchers collected temperature data from 44 shallow water wells and 9 oil wells up to 2500m deep to determine surface heat flow density. They also measured thermal conductivities of rock samples. Temperature profiles in the shallow wells showed nonlinear increases with depth likely due to water movement. Repeated measurements over a year showed stable temperature distributions. Heat flow density varied regionally from 35 to 115 mW/m2, with a mean of 60 mW/m2. Higher values were found in areas of active extension south of the Marmara Sea. The spatial pattern of thermal springs did not coincide with heat flow patterns, as their appearance
This geomechanical model investigates the 3D kinematics of the fault system beneath the Marmara Sea region in northwest Turkey. The model incorporates the recently imaged fault structures below the Marmara Sea as frictional surfaces. It is subjected to gravity and kinematic boundary conditions derived from observations. The model results agree with GPS velocities, geological fault slip rates, palaeomagnetic measurements and patterns of subsidence and uplift. The Main Marmara Fault can be interpreted as a through-going strike-slip fault, but there is also significant dip-slip motion locally. Sensitivity analysis shows rock properties and initial stress have minor influence on kinematics, whereas the 3D fault structure is the key control. The modeled slip rate of the
The document discusses well logging techniques. It begins by defining a well log as a continuous record of measurements made in a borehole that respond to variations in physical rock properties. It then discusses the concept of borehole invasion, where drilling mud contaminates the formation near the borehole. Key logging tools are described, including gamma ray, spontaneous potential, resistivity, density, neutron, and sonic logs. Porosity calculations using various logs are also presented. In particular, it focuses on how well logs can be used to determine lithology, porosity, fluid content and hydrocarbon saturation in geological formations.
The document provides information about well logging techniques. It discusses how the borehole and surrounding rock can be invaded by drilling mud, affecting measurements. It describes the invaded zone and different resistivity measurements that can be taken. It then discusses various well logging tools - gamma ray, spontaneous potential, resistivity, density, neutron, and sonic logs - and how they are used to evaluate properties like lithology, porosity, fluid content, and hydrocarbon saturation.
The document discusses digital logic design and covers the following topics in 3 sentences:
It introduces basic concepts in digital logic like logic gates, truth tables, and complete gate sets. It then discusses combinational logic circuits like multiplexers, demultiplexers, decoders, comparators, and adders. Finally, it discusses sequential circuits and arithmetic logic units that can perform arithmetic and logical operations on binary numbers.
The document discusses refraction seismology field work. It covers types of seismometers used, how a refraction survey is set up with geophone spreads and shot locations, and controlled seismic sources like impact and vibrating sources. An example refraction profile from Santa Teresa Hills is shown and discussed, including determining intercept times and velocities to develop a geophysical model of subsurface layers. Students are assigned a field study report on their refraction data due next month.
The document discusses concepts in gravity and isostasy from an introduction to geophysics course. It covers topics like gravity units, sensitivity to mass changes, density of geological materials, examples of gravity maps, isostatic equilibrium, bouguer anomalies over land and sea, and an example from Arabia. It also provides homework instructions to make an online gravity map and define terms in an equation related to gravity concepts.
This document provides an overview of a well logging course, including the course objectives, structure, and assessment criteria. The course aims to provide both theoretical and practical training in well logging through lectures, class projects, and a final exam. Key topics that will be covered include gamma ray logging, potential logging, acoustic logging, density logging, and mud logging. Students will be expected to demonstrate understanding of well logging tools, principles, and applications by the end of the course. Their performance will be evaluated based on participation, projects, and a closed-book final exam.
The document discusses gravity methods in geophysics. It provides examples of gravity measurements and calculations, including Bouguer corrections on land and sea. It also discusses different units used to measure gravitational acceleration and explains the use of milligals for small measurements like on Phobos.
This document discusses seismic wave travel time models for both flat and curved earth models. It explains that for a flat earth model with distinct layers, seismic rays emerge at steeper angles with increasing depth, changing the slope of first arrivals. A model with numerous thin layers is approximated as a continuous velocity function of depth. For a curved earth model, rays bend away from vertical, leading to steeper emergence angles and more curved travel time graphs, indicating higher apparent velocities than for a constant velocity flat earth model.
The document discusses isostasy and models of crustal compensation. It describes Airy and Pratt models of isostatic equilibrium, where topography is supported by either lateral density variations within the crust (Pratt model) or variations in crustal thickness (Airy model). Continental collision leads to the highest elevations on Earth because the thick, buoyant continental crust uplifts vast areas when plates converge.
Isostasy refers to the equilibrium between blocks of Earth's crust and the underlying mantle. Lighter crustal blocks "float" higher, while heavier blocks sink deeper into the mantle. There are three models of isostasy: the Airy-Heiskanen model where crustal thickness changes with topography; the Pratt-Hayford model where lateral density changes accommodate topography; and the flexural isostasy model where the lithosphere bends under local loads. Deposition and erosion affect isostatic equilibrium as crust rises when loaded and sinks when unloaded, like an iceberg. Plate tectonics and ice sheets also impact isostasy through crustal thickening during collisions and post-gl
This document discusses seismic refraction analysis, which uses the transmission of seismic waves through different subsurface layers to determine layer properties and depths. It explains key concepts like Snell's law, critical refraction angles, and travel time distance curves. The document also lists applications of seismic refraction including determining depths of weathering zones, groundwater tables, basements, Moho discontinuity, and faster subsurface units.
This document provides an overview of geophysical data analysis and seismic wave theory. It defines key terms like body waves, surface waves, reflection, refraction, and diffraction. Body waves include compressional P-waves and shear S-waves, while surface waves are Rayleigh and Love waves. Reflection, refraction, and diffraction occur when seismic waves encounter interfaces between layers with different velocities. Multiples and ghosts are examples of phenomena that can complicate seismic data analysis if not properly handled. The document aims to give theoretical background knowledge needed to understand seismic data.
Reservoir Geophysics : Brian Russell Lecture 1Ali Osman Öncel
This document provides an introduction to AVO and pre-stack inversion methods. It begins with a brief history of seismic interpretation, from purely structural interpretation to identifying "bright spots" to direct hydrocarbon detection using AVO and pre-stack inversion. It then discusses how AVO response is closely linked to rock physics properties like P-wave velocity, S-wave velocity, and density. The key concepts of AVO modeling and attributes are introduced. Finally, it provides an overview of rock physics and fluid replacement modeling using equations like Biot-Gassmann to model velocity and density changes with fluid saturation.
Gravimetry uses measurements of variations in Earth's gravitational field to obtain information about subsurface density variations. It has applications in hydrocarbon exploration, geological mapping, and other fields. Gravity measurements are based on Newton's law of universal gravitation. Instruments used include stable gravimeters like pendulums and torsion balances, as well as portable unstable gravimeters. Measurements require corrections for factors like latitude, altitude, tides and drift. Density differences between rock types are the source of gravitational anomalies that can be interpreted.
Reservoir Geophysics : Brian Russell Lecture 2Ali Osman Öncel
This document discusses Amplitude Variation with Offset (AVO) techniques and impedance inversion methods. It covers the basics of AVO modeling using the Zoeppritz, Aki-Richards, and Fatti equations. The key methods are described, including intercept-gradient analysis and modeling AVO classes. Examples are provided to illustrate modeling reflections from wet versus gas sands and comparing the different AVO modeling approaches.
The document provides an overview of principles of seismic data interpretation. It discusses fundamentals of seismic acquisition and processing such as seismic response, phase, polarity, reflections, and resolution. It also covers topics like structural interpretation pitfalls, seismic interpretation workflows involving building databases and time-depth relationships, and structural styles. The document includes sections on depth conversion, subsurface mapping techniques, and different types of velocities.
This geomechanical model investigates the 3D kinematics of the fault system beneath the Marmara Sea region in northwest Turkey. The model incorporates the recently imaged fault structures below the Marmara Sea as frictional surfaces. It is subjected to gravity and kinematic boundary conditions derived from observations. The model results agree with GPS velocities, geological fault slip rates, palaeomagnetic measurements and patterns of subsidence and uplift. The Main Marmara Fault can be interpreted as a through-going strike-slip fault, but there is also significant dip-slip motion locally. Sensitivity analysis shows rock properties and initial stress have minor influence on kinematics, whereas the 3D fault structure is the key control. The modeled slip rate of the
The document discusses well logging techniques. It begins by defining a well log as a continuous record of measurements made in a borehole that respond to variations in physical rock properties. It then discusses the concept of borehole invasion, where drilling mud contaminates the formation near the borehole. Key logging tools are described, including gamma ray, spontaneous potential, resistivity, density, neutron, and sonic logs. Porosity calculations using various logs are also presented. In particular, it focuses on how well logs can be used to determine lithology, porosity, fluid content and hydrocarbon saturation in geological formations.
The document provides information about well logging techniques. It discusses how the borehole and surrounding rock can be invaded by drilling mud, affecting measurements. It describes the invaded zone and different resistivity measurements that can be taken. It then discusses various well logging tools - gamma ray, spontaneous potential, resistivity, density, neutron, and sonic logs - and how they are used to evaluate properties like lithology, porosity, fluid content, and hydrocarbon saturation.
The document discusses digital logic design and covers the following topics in 3 sentences:
It introduces basic concepts in digital logic like logic gates, truth tables, and complete gate sets. It then discusses combinational logic circuits like multiplexers, demultiplexers, decoders, comparators, and adders. Finally, it discusses sequential circuits and arithmetic logic units that can perform arithmetic and logical operations on binary numbers.
The document discusses refraction seismology field work. It covers types of seismometers used, how a refraction survey is set up with geophone spreads and shot locations, and controlled seismic sources like impact and vibrating sources. An example refraction profile from Santa Teresa Hills is shown and discussed, including determining intercept times and velocities to develop a geophysical model of subsurface layers. Students are assigned a field study report on their refraction data due next month.
The document discusses concepts in gravity and isostasy from an introduction to geophysics course. It covers topics like gravity units, sensitivity to mass changes, density of geological materials, examples of gravity maps, isostatic equilibrium, bouguer anomalies over land and sea, and an example from Arabia. It also provides homework instructions to make an online gravity map and define terms in an equation related to gravity concepts.
This document provides an overview of a well logging course, including the course objectives, structure, and assessment criteria. The course aims to provide both theoretical and practical training in well logging through lectures, class projects, and a final exam. Key topics that will be covered include gamma ray logging, potential logging, acoustic logging, density logging, and mud logging. Students will be expected to demonstrate understanding of well logging tools, principles, and applications by the end of the course. Their performance will be evaluated based on participation, projects, and a closed-book final exam.
The document discusses gravity methods in geophysics. It provides examples of gravity measurements and calculations, including Bouguer corrections on land and sea. It also discusses different units used to measure gravitational acceleration and explains the use of milligals for small measurements like on Phobos.
This document discusses seismic wave travel time models for both flat and curved earth models. It explains that for a flat earth model with distinct layers, seismic rays emerge at steeper angles with increasing depth, changing the slope of first arrivals. A model with numerous thin layers is approximated as a continuous velocity function of depth. For a curved earth model, rays bend away from vertical, leading to steeper emergence angles and more curved travel time graphs, indicating higher apparent velocities than for a constant velocity flat earth model.
The document discusses isostasy and models of crustal compensation. It describes Airy and Pratt models of isostatic equilibrium, where topography is supported by either lateral density variations within the crust (Pratt model) or variations in crustal thickness (Airy model). Continental collision leads to the highest elevations on Earth because the thick, buoyant continental crust uplifts vast areas when plates converge.
Isostasy refers to the equilibrium between blocks of Earth's crust and the underlying mantle. Lighter crustal blocks "float" higher, while heavier blocks sink deeper into the mantle. There are three models of isostasy: the Airy-Heiskanen model where crustal thickness changes with topography; the Pratt-Hayford model where lateral density changes accommodate topography; and the flexural isostasy model where the lithosphere bends under local loads. Deposition and erosion affect isostatic equilibrium as crust rises when loaded and sinks when unloaded, like an iceberg. Plate tectonics and ice sheets also impact isostasy through crustal thickening during collisions and post-gl
This document discusses seismic refraction analysis, which uses the transmission of seismic waves through different subsurface layers to determine layer properties and depths. It explains key concepts like Snell's law, critical refraction angles, and travel time distance curves. The document also lists applications of seismic refraction including determining depths of weathering zones, groundwater tables, basements, Moho discontinuity, and faster subsurface units.
This document provides an overview of geophysical data analysis and seismic wave theory. It defines key terms like body waves, surface waves, reflection, refraction, and diffraction. Body waves include compressional P-waves and shear S-waves, while surface waves are Rayleigh and Love waves. Reflection, refraction, and diffraction occur when seismic waves encounter interfaces between layers with different velocities. Multiples and ghosts are examples of phenomena that can complicate seismic data analysis if not properly handled. The document aims to give theoretical background knowledge needed to understand seismic data.
Reservoir Geophysics : Brian Russell Lecture 1Ali Osman Öncel
This document provides an introduction to AVO and pre-stack inversion methods. It begins with a brief history of seismic interpretation, from purely structural interpretation to identifying "bright spots" to direct hydrocarbon detection using AVO and pre-stack inversion. It then discusses how AVO response is closely linked to rock physics properties like P-wave velocity, S-wave velocity, and density. The key concepts of AVO modeling and attributes are introduced. Finally, it provides an overview of rock physics and fluid replacement modeling using equations like Biot-Gassmann to model velocity and density changes with fluid saturation.
Gravimetry uses measurements of variations in Earth's gravitational field to obtain information about subsurface density variations. It has applications in hydrocarbon exploration, geological mapping, and other fields. Gravity measurements are based on Newton's law of universal gravitation. Instruments used include stable gravimeters like pendulums and torsion balances, as well as portable unstable gravimeters. Measurements require corrections for factors like latitude, altitude, tides and drift. Density differences between rock types are the source of gravitational anomalies that can be interpreted.
Reservoir Geophysics : Brian Russell Lecture 2Ali Osman Öncel
This document discusses Amplitude Variation with Offset (AVO) techniques and impedance inversion methods. It covers the basics of AVO modeling using the Zoeppritz, Aki-Richards, and Fatti equations. The key methods are described, including intercept-gradient analysis and modeling AVO classes. Examples are provided to illustrate modeling reflections from wet versus gas sands and comparing the different AVO modeling approaches.
The document provides an overview of principles of seismic data interpretation. It discusses fundamentals of seismic acquisition and processing such as seismic response, phase, polarity, reflections, and resolution. It also covers topics like structural interpretation pitfalls, seismic interpretation workflows involving building databases and time-depth relationships, and structural styles. The document includes sections on depth conversion, subsurface mapping techniques, and different types of velocities.
Beklenen İstanbul Depremlerinin geçmişte Adalara yakın olduğu gibi gelecekte adalara yakın olabileceği sürekli tartışılır. İlk defa Adalarda "İstanbul Depremi ve Adalar Oturumu" JFMO İstanbul Şube tarafından organize edildi ve bu organizasyon için 18 Eylül 1963 M6.3 Adalar depreminden 50 Yıl sonra gerçekleşti. Katılım çok iyiydi ve Jeofizik Mühendisi Deprem Uzmanları Adalı yaşayanlara depremle ilgili gerçekleri bilimsel verilerle açıklamaya çalıştı. Halkın diliyle Bilim İnsanının dili arasında ki farktan dolayı toplantı sürecinde anlaşılmayan kısımlar oldu ve bu kısımlar sorularla giderildi. Jeofizik Mühendisleri Deprem Uzmanları Adalı Yaşayanlarla Yüzleştiği İlk ve Tek Toplantı olarak yapılan organizasyon TARİHE GEÇTİ. JFMO İstanbul Şube düzenlediği bir toplantıyla TARİH YAZDI dense abartı sayılmamalı çünkü Adalar Tarihinde Yaşayan Adalılarla Jeofizik Mühendisi Bilim Uzmanlarının ÖZEL DEPREM OTURUMUNDA ilk yüzleşmesiydi
Gravimetri Dersi için aşağıda ki videoları izleyebilirsiniz.
Link 01: https://www.youtube.com/watch?v=HTyjVaVGx0k
Link 02: https://www.youtube.com/watch?v=fUkfgI8XaOE
The document discusses gravity anomalies and density variations in different regions based on gravity data. It shows how gravity maps reveal details about crustal thickness, tectonic features like faults and volcanic zones, and plate boundaries. Specific examples discussed include the Tibetan Plateau, Central America subduction zone, an area in Chugoku, Japan, and the state of Florida in the US. Regional gravity data can be used to model density changes associated with plate tectonics, crustal evolution, and volcanic and tectonic activity.
The USF team reviewed a geophysical investigation of the Kar Kar region conducted by WesternGeco in 2011. They found that WesternGeco's magnetotelluric (MT) data and models were of high quality. Both the WesternGeco and USF MT models identified a low resistivity zone at 300m depth that correlates with a water-bearing zone found in Borehole 4. USF performed gravity modeling which identified a north-south trending basin reaching 1500m depth, consistent with mapped faults. A preliminary hydrothermal model suggested observed temperatures could result from deep circulation of meteoric waters in the basin without needing a localized heat source. Additional geophysical data is recommended around the Jermaghbyur hot springs to
This document summarizes a study that used gravity data to delineate underground structure in the Beppu geothermal field in Japan. Analysis of Bouguer anomaly maps revealed high anomalies in the southern and northern parts of the study area that correspond to known geological formations. Edge detection filtering of the gravity data helped identify subsurface faults, including the northern edge of the high southern anomaly corresponding to the Asamigawa Fault. Depth modeling of the gravity basement showed differences between the southern and northern hot spring areas, with steep basement slopes along faults in the south and uplifted basement in the north.
This document summarizes the development of a new ultra-high resolution model of Earth's gravity field called GGMplus. Key points:
- GGMplus combines satellite gravity data from GOCE and GRACE with terrestrial gravity data and topography to achieve unprecedented 200m spatial resolution globally.
- It provides gridded estimates of gravity, horizontal and radial field components, and quasi-geoid heights at over 3 billion points covering 80% of the Earth's land.
- GGMplus reveals new details of small-scale gravity variations and identifies locations of minimum and maximum gravity, suggesting peak-to-peak variations are 40% larger than previous estimates. The model will benefit scientific and engineering applications.
Gravity measurements were taken in a region of China covering the south-north earthquake belt in 1998, 2000, 2002, and 2005. Researchers noticed significant gravity changes in the region surrounding Wenchuan and suggested in 2006 that a major earthquake could occur there in 2007 or 2008. While gravity changes were significant at some locations, more research is needed to determine if they could be considered a precursor. Uncertainties exist from measurement errors, hydrologic effects, and crustal movements. Improved data collection and analysis could enhance using gravity monitoring for earthquake research.
The document provides guidelines for implementing the H/V spectral ratio technique using ambient vibration measurements to evaluate site effects. It recommends procedures for experimental design, data processing, and interpretation. The key recommendations include measuring for sufficient duration depending on expected frequency, using multiple measurement points, avoiding disturbances, and interpreting H/V peaks in context with geological and geophysical data. Reliable H/V peaks are defined as having a clear maximum within expected frequency ranges and uncertainties. The guidelines aim to help apply the technique while accounting for its limitations.
Geopsy yaygın olarak kullanılan profesyonel bir program. Özellikle, profesyonel program deneyimi yeni mezunlarda çok aranan bir özellik. Bir öğrencim çalışmasında kullanmayı planlıyor.
1. Görüntü kalitesi ve kapsamı kaynağa
ve kayıtçıya bağlıdır.
Jeofizik Mühendisliği Bölümü
İstanbul Üniversitesi
Prof. Dr. Ali Osman Öncel
aliosman.oncel@gmail.com
Saha SismolojisiSaha Sismolojisi
http://www.istanbul.edu.tr/mb/fieldGeo/sismoloji.htmlhttp://www.istanbul.edu.tr/mb/fieldGeo/sismoloji.html
7. Darbeli kaynaklar Patlatmalı Kaynaklar
Sismik dalgalar farklı kaynak türleriyle üretilirler:
Ağırlık-düşürmeli kaynaklar (örnek. Çelik plaka üzerine çekiçle vurarak)
Titreşimli ağırlık düşürme
Titreşimli kaynaklar (‘vibroseis’)
Patlayıcılar (dinamit, aşağı atışlı tabanca)
Titreşimli
8. Düşük hız tabakalı ortamda yer incelemesi
yapılırken, yarım tonluk yükün yere
düşürülmesi.
Darbeli kaynak kullanımı yüzlerce kg
ağırlığındaki malzemenin traktör yada vinç
türü araçlarla yere bırakılmasıdır.
29. Deprem sismolojisi ile Arama
sismolojisi yöntem olarak aynıdır
fakat kaynak bakımından biri doğal
diğeri yapay kaynaklıdır. Yüzlerce
depreme ait veriler analiz edilir. Bu
yolla çalışılan alanın hız yapısı
belirlenir. Sismik tomografi yöntemi
sismik dalgaları üç boyutlu kayıtçı
sistemi ile kayıt etmektedir.
30. Tomografi Yönteminin Amaçları
GtrtfÌ`eh p`yÌ`r ƒdÌ h±hshsı
v b`pq p yd ptrËt„hvƒts cd h hrhshı ı ğ ş
tÌw`ƒ` ptƒ`Ì
Tomografi yönteminin Sismolojideki amacı:
Mantonun en sıcak ve soğuk bölümlerini bulmak,
Manto içindeki konveksiyon akımlarının akış
yönünü belirlemek,
Çekirdek ve manto sınırındaki vadi dağ yapısını
belirlemektir.
31. Tomografi yöntemi lokal ve global olmak üzere ikiye
ayrılmaktadır. Lokal tomografiye örnek verecek olursak bir
bölgede deprem meydana geldikten hemen sonra bu bölgeye
yerleştirdiğimiz kayıtçı yardımı ile artçı depremler ve yer
içindeki hız değişimi belirlenebilir.
Lokal Tomografi: 3 boyutlu kabuk
çalışmalarında kaynak ve alıcı
birlikte bulunur.
Global Tomografi: Tüm dünyanın
değişik yerlerinden gelen kaynağın
yeri ve yönü belirli değildir.
Modified after from Dr. Stephan Husen’s lecture
notes
35. Sismik görüntüleme çok aktif ve
popüler bir çalışma alanıdır. Bu
nedenle, bu alanda çalışanların
önü açıktır.
36. 1800’s view of Earth
KRAEMER (1902)
1903’s view of Earth
BOLT (Inside the Earth, 1973)
1973’s view of Earth
DZIEWONSKI (~1990, from www)
1999’s view of Earth
Yerin İçinin Hakkında Bilgi Nereden Geliyor?
37. Deprem sismolojisi ile Arama
sismolojisi yöntem olarak aynıdır
fakat kaynak bakımından biri doğal
diğeri yapay kaynaklıdır. Yüzlerce
depreme ait veriler analiz edilir. Bu
yolla çalışılan alanın hız yapısı
belirlenir. Sismik tomografi yöntemi
sismik dalgaları üç boyutlu kayıtçı
sistemi ile kayıt etmektedir.
40. Sismik Görüntülemede hangi veriler kullanılır?
Seyahat zamanı tomografisi (P ve S), tele-sismik verilerin ilk
varış değerlerini kullanır.
Modified after from Dr. Stephan Husen’s lecture notes
M4 earthquake close to Brugg, Station DAVOX
41. Global Tomografi Nedir?
Telesismik dalgalar uzaktan gelen geniş periyotlu dalgalardır.Bunları kayıt etmek
için geniş periyotlu kayıtçılara ihtiyacımız vardır. Telesismik tomografi ile kaydedilen
yerin altı ile ilgili bilgi toplayabilmekteyiz. Hedefleri: Bulunulan alanın altındaki
mantonun alt ve üst yapısını belirlemek, dalan bir levhanın indiği derinliği bulmak,
kıtaların köklerinin nereye kadar gittiğinin tespiti vs.
Çalışma alanı
istasyonlar
deprem
57. Field Trip: KFUPM BEACH
Purpose: Refraction Seismology
Acknowledgement: I appreciate Dr.Al-Shaibani who provided a huge
support for us to make a field trip. Extend to my appreciation to
Dr.Korvin who made very good suggestion in the course of selecting
area, as well as Mr. Mohamed Ahmed who prepared timely things
which are needed for trip. Dr. Satish Pullammanappallil, from the
company of OptimSoftware in Reno City of USA, who helped me the
picking up the first arrivals of P-wave and 2D modeling field-
measured refraction data by SeisOpt @2D as well as the 1D model of
shear-wave velocities by SeisOpt ReMi and provided invaluable
continuous discussion for future work.
58. Kırılma Tomografisi İçin
İdeal Saha Modeli Nedir?
Shot 2
16.9m
Shot 1 Shot 4Shot 3 Shot 6Shot 5 Shot 7
16.9m
15 m 15 m
Kırılma modellemesi için ideal açılım:
Jeofonlar sabit tutulur ve atış noktaları değiştirilir.
Çok-atışlı veriye bağlı olarak kırılma tomografisi
yapılır.
62. Bazı Notlar
• Kırılma profillerinin sayısının artırılması ve vuruş sayısının
arttırılması ile 2D Sismik görüntüleme kalitesi arttırılabilir.
Sismik tomografi çalışmalarında kullanılan bir çok program
vardır, bu programlardan, SeisOpt @2D bu ders kapsamında
anlatılacaktır.
• Saha sismolojisi uygulamalarında, yüksek örnekleme aralığı
(0.125ms or 0.25ms) and 2 saniyelik kayıt uzunluğu gerekir.
Editor's Notes
Gerçek
Önceki Ders
Hatalı Sonuç
Impact Sources, Vibrating
Impact source. A half-ton weight being dropped from a portable crane during a survey of the low-velocity layer.
More powerful impact sources must be used in larger surveys. Weights of hundreds of kilograms can be raised by portable hoists or cranes and then dropped (Figure 11.3). The minimum release height is about 4 m, even if a shorter drop would provide ample energy, since rebound of the support when the weight is released creates its own seismic wavetrain. A long drop allows these vibrations to die away before the impact occurs. Tractor-mounted posthole drivers, common in farming areas, are also convenient sources. The weight drops down a guide and is raised by a pulley system connected to the tractor power take-off. Relatively small (70 kg) weights falling in evacuated tubes have sometimes been used. The upper surface of the weight is exposed to the air, and effectively several hundred extra kilograms of atmosphere are also dropped. The idea is elegant but the source is difficult to transport because the tube must be strong and therefore heavy and must be mounted on a trailer, together with a motor-driven compressor to pump out the air. Vibration sources are widely used in large-scale reflection surveys but produce data that need extensive and complex processing.
be known. In some instruments this appears on the record as a break in one of the traces (the shot break or time break). On most modern instruments it actually defines the start of the record. Time-break pulses may be produced in many different ways. A geophone may be placed close to the source, although this is very hard on the geophone.
Explosive sources are usually fired electrically, and the cessation of current flow in the detonator circuit can provide the required signal. Alternatively, a wire can be looped around the main explosive charge, to be broken at the shot instant. This technique can be used on the rare occasions when charges are fired using lit fuses. Hammer surveys usually rely on making rather than breaking circuits. One method is to connect the hammer head to one side of the trigger circuit and the plate (assuming it is metal, not rubber) to the other. Although this sounds simple and foolproof, in practice the repeated shocks suffered by the various connections are too severe for long-term reliability. In any case, the plates themselves have rather short lives, after which new connections have to be made. It is more practical to mount a relay on the back of the hammer handle, just behind the head, that closes momentarily when the hammer hits the plate (Figure 11.4). It will close late, or not at all, if the hammer is used the wrong way round. Solid-state switches sold by some seismograph manufacturers give more repeatable results but are expensive and rather easily damaged. The cable linking the trigger switch on a hammer to the recorder is always vulnerable, tending to snake across the plate just before impact. If it is cut, the culprit is traditionally required both to repair the damage and ease the thirst of all the witnesses!
Balyoz ile çalışma yaparken bloğa yandan vurulduğunda
S dalgası elde edilir.Yukarıdan vurulduğunda ise P dalgası elde edilir
Moving coil geophone. Hareketli Bobin
A geophone consists of a coil wound on a high-permeability magnetic core and suspended by leaf springs in the field of a permanent magnet (Figure 11.6). If the coil moves relative to the magnet, voltages are induced and current will flow in any external circuit. The current is proportional to the velocity of the coil through the magnetic field, so that ground movements are recorded, not ground displacements. In most cases the coil is mounted so that it is free to vibrate vertically, since this gives the maximum sensitivity to P waves rising steeply from subsurface interfaces, i.e. to reflected and refracted (but not direct) P waves. P-wave geophones that have been normally connected give negative first-arrival pulses (breaks) for refractions and reflections, but may break either way for direct waves. In reflection work using large offsets, or in refraction work where the velocity contrasts between overburden and deeper refractors are small, the rising wavefronts make relatively large angles with the ground surface and the discrimination by the geophones between S waves and P waves will be less good.
Figure 11.8 Geophone carrying frame in use, Papua New Guinea.
Geophones are remarkably rugged, which is just as well considering the ways in which they are often treated. Even so, their useful lives will be
reduced if they are dumped unceremoniously from trucks into tangled heaps on the ground. Frames can be bought or made to which they can be clipped
for carrying (Figure 11.8) and these can be good investments, but only if actually used.
Figure 11.9 Enhancement seismographs. The instrument on the right is the now obsolete knob and switch controlled Geometrics 1210F. The instrument on the left is one of its successors, the Smartseis, which is entirely menu-driven. Note the hard-copy record just emerging from the Smartseis, and the much greater size of the display ‘window’.
The enhancement seismographs now in use (Figure 11.9) are very sophisticated and versatile instruments. Display formats can be varied and individual traces can be selected for enhancement, replacement or preservation. Traces can be amplified after as well as before storage in memory, and time offsets can be used to display events that occur after long delay times.
Figure 12.2 Enhancement seismograph record showing curved alignment of reflections (thick line). The earlier events were produced by refractions. Note that on Channels 11 and 12 the strong refracted wave completely overwrites the reflection. The variable area presentation used is popular for reflection work since it emphasizes trace-to-trace correlations, although some information is lost where traces overlap.
İÜ Mühendislik Bilimleri Bölümü ve Seismic Source Şirketi Antlaşmalıdır.
Yeterli veri sayısına ulaşıldığında bu istasyondan yerin altına doğru hız değişimi görüntülenebilir. Modified after from Dr. Stephan Husen’s lecture notes