The document outlines the academic and teaching experiences of Ali O. Oncel. It discusses his work teaching both graduate and undergraduate courses in geophysics online. It also mentions his research involving seismicity patterns, fault statistics, and analyzing the relationship between seismic activity, strain rates, and fluid saturation using field experiments.
A basic introduction to available geophysical test methods for the use of Geotechnical engineers presented at the USACE Infrastructure Conference in Atlanta, June 2011.
Deprem Verilerinin H/V Oranının Mevsimsel Değişimi Ali Osman Öncel
H/V oranının zaman içinde değişimi konusu bana oldukça ilginç gelmişti ve bu tür bir çalışma yapıldı mı sorusunu netleştirmek için araştırma yaptım ve 2021 yılında bu konuda GJI gibi bir dergide yayınlanmış bir çalışma buldum. Bu çalışma oldukça iyi bir referans H/V çalışmaları için. Önemli referans düşünceler şöyle; 1) Mevsimsel olarak yağışa bağlı olarak yeraltı kaynaklarında ki azalma ve yükselmeye bağlı olarak H/V yükseliyor, 2) H/V pik değerleri kaya zemin üzerinde yaklaşık BİR (1) oranında seyreder ve PİK vermezken, kaya zeminden uzaklaşıldıkça zemin etkisi ile PİK değerleri değişir, 3) Deprem ve Gürültü sinyallerinden hesap edilen F(PİK) nerede ise sabitken, H/V oranları %10 değişir, 4) M6.8 büyüklüğünde meydana gelen bir deprem H/V değişimlerini etkiler.
Yapılan çalışmada kullanılan yaklaşım SESAME (2004) kriterlerine uygun olarak 1) 60 dakikalık veriler analizi, 2) 1000 günden fazla gözlem süresi 3) 10'dan fazla farklı zeminlerde istasyon 4) 60 dakikalık birbirinden ayrı verilerin analiz edilmesi. Oldukça emek yoğun bir çalışma
M6.0 2004 Parkfield Earthquake : Seismic AttenuationAli Osman Öncel
HRSN isimli kuyu içi sismik istasyonlar kullanılarak, San Andreas fayı boyunca meydana gelen büyük depremler öncesi sismik azalımın varlığının olup olmadığı araştırılıyor.
Gravity and magnetic methods are an essential part of oil exploration. They do not replace seismic. Rather, they add to it. Despite being comparatively low-resolution, they have some very big advantages.
These geophysical methods passively measure natural variations in the earth’s gravity and magnetic fields over a map area and then try to relate these variations to geologic features in the subsurface. Lacking a controlled source, such surveys are usually environmentally unobjectionable.
A basic introduction to available geophysical test methods for the use of Geotechnical engineers presented at the USACE Infrastructure Conference in Atlanta, June 2011.
Deprem Verilerinin H/V Oranının Mevsimsel Değişimi Ali Osman Öncel
H/V oranının zaman içinde değişimi konusu bana oldukça ilginç gelmişti ve bu tür bir çalışma yapıldı mı sorusunu netleştirmek için araştırma yaptım ve 2021 yılında bu konuda GJI gibi bir dergide yayınlanmış bir çalışma buldum. Bu çalışma oldukça iyi bir referans H/V çalışmaları için. Önemli referans düşünceler şöyle; 1) Mevsimsel olarak yağışa bağlı olarak yeraltı kaynaklarında ki azalma ve yükselmeye bağlı olarak H/V yükseliyor, 2) H/V pik değerleri kaya zemin üzerinde yaklaşık BİR (1) oranında seyreder ve PİK vermezken, kaya zeminden uzaklaşıldıkça zemin etkisi ile PİK değerleri değişir, 3) Deprem ve Gürültü sinyallerinden hesap edilen F(PİK) nerede ise sabitken, H/V oranları %10 değişir, 4) M6.8 büyüklüğünde meydana gelen bir deprem H/V değişimlerini etkiler.
Yapılan çalışmada kullanılan yaklaşım SESAME (2004) kriterlerine uygun olarak 1) 60 dakikalık veriler analizi, 2) 1000 günden fazla gözlem süresi 3) 10'dan fazla farklı zeminlerde istasyon 4) 60 dakikalık birbirinden ayrı verilerin analiz edilmesi. Oldukça emek yoğun bir çalışma
M6.0 2004 Parkfield Earthquake : Seismic AttenuationAli Osman Öncel
HRSN isimli kuyu içi sismik istasyonlar kullanılarak, San Andreas fayı boyunca meydana gelen büyük depremler öncesi sismik azalımın varlığının olup olmadığı araştırılıyor.
Gravity and magnetic methods are an essential part of oil exploration. They do not replace seismic. Rather, they add to it. Despite being comparatively low-resolution, they have some very big advantages.
These geophysical methods passively measure natural variations in the earth’s gravity and magnetic fields over a map area and then try to relate these variations to geologic features in the subsurface. Lacking a controlled source, such surveys are usually environmentally unobjectionable.
is one of the first steps in
searching for oil and gas resources that directly
affects the land and the landowners Seismic surveys are like sonar on steroids They are based on recording the time it takes for sound waves generated by controlled energy sources .The survey usually requires people and machinery
to be on private property and may result in
disturbances of the land such as the clearing of
trees
Anatomy of a Megathrust Earthquake Rupture - The 2010 M8.8 Chile QuakeStephen Hicks
Presented for an IRIS (Incorporated Research Institutions for Seismology) webinar on 9 April 2014.
Webinar can be viewed here: https://www.youtube.com/watch?v=MNcl5AZlX3k
Abstract: In February 2010, a magnitude 8.8 megathrust earthquake struck the Maule region of Central Chile - the sixth largest earthquake ever recorded. It is fast becoming one of the best-studied megathrust ruptures, allowing us a unique insight into the inner workings of subduction zone earthquakes. In the earthquake’s immediate aftermath, an international group of research institutions deployed geophysical instruments in the rupture area. A network of ~160 seismic stations on the forearc recorded over 50,000 aftershocks in the first 10 months following the earthquake.
I have used observations of P- and S-waves from aftershocks to derive a high-resolution seismic travel-time tomography of the rupture zone. Observations from ocean-bottom seismometers further improve image sharpness in the offshore portion of the seismogenic zone, where most slip occurred during the earthquake. The tomographic images reveal the distribution of P-wave velocity and Poisson’s Ratio within the earthquake rupture zone. Based on accurate aftershock locations and moment tensors, I have defined a new 3-D plate interface geometry to infer the physical structure and composition along the plate interface. I compare these velocities with the mainly geodetically observed behaviour of the fault throughout a cycle of seismic behaviour (preseismic locking, coseismic slip, postseismic deformation). This comparison allows us to understand some of the physical properties that may govern seismogenesis along the megathrust. I will reveal how both the long-lived geological structure of the forearc and the composition of the subducting oceanic plate may influence the rupture behaviour of large megathrust earthquakes. An understanding of seismic velocities along the megathrust may therefore be used to constrain the seismogenic potential of subduction zones worldwide.
PetroTeach Free Webinar by Dr. Andrew Ross on Seismic Reservoir CharacterizationPetro Teach
A reliable reservoir model is an invaluable tool for risk reduction. I will give an overview of seismic reservoir characterization and the quantitative interpretation workflow including the use of pre and post stack seismic attributes and inversion outputs for mapping reservoir properties and integration of the attribute output with petrophysical data to create quantitative reservoir models.
PetroTeach Free Webinar on Seismic Reservoir CharacterizationPetroTeach1
A reliable reservoir model is an invaluable tool for risk reduction. Dr. Andrew Ross gave an overview of seismic reservoir characterization and the quantitative interpretation workflow including the use of pre and post-stack seismic attributes and inversion outputs for mapping reservoir properties and integration of the attribute output with petrophysical data to create quantitative reservoir models.
A New geotechnical method for Natural slope exploration and analysisRasika Athapaththu
Geotechnical investigation of natural slopes is challengeable especially whennatural slopes having higher gradients and access is difficult. Also, it is even more problematic to find the shear strength parameters spatially to evaluate the stability of slopes as most of the methods available to find the shear strength parameters in the literature are uneconomical or such methods cannot be applied in vegetated slopes. Recently, authors have conducted a series of in-situ investigations based on the newly developed.....
A new geotechnical method for natural slope exploration and analysis Rasika Athapaththu
Geotechnical investigation of natural slopes is challengeable especially whennatural slopes having higher gradients and access is difficult. Also, it is even more prob-lematic to find the shear strength parameters spatially to evaluate the stability of slopes asmost of the methods available to find the shear strength parameters in the literature areuneconomical or such methods cannot be applied in vegetated slopes. Recently, authorshave conducted a series of in situ investigations based on the newly developed
A New Geotechnical Method for natural Slope Exploration and AnalysisRasika Athapaththu
.............Therefore, a new field test technique is required to assess the natural slopes havingdense vegetation to overcome the shortcomings of the existing methods. The charac-teristics of the proposing technique have to be lightweight, economical, safe, and reli-able. With this aim, the academics and the researchers in geotechnical laboratory of Hiroshima University, Japan, have experimented a new field method based on dynamiccone penetrometers: recently introduced ......................
Geophysical methods in Hydrocarbon ExplorationRaboon Redar
Geophysical studies of the earth's interior include measurements on or near to the earth's surface that are dependent upon the physical properties of the internal distribution. Examination of these measurements can show how vertically and laterally the physical properties of the Earth's interior differ. Through operating on different scales, geophysical techniques can be used to investigate the localized upper crust area for engineering or other purposes.
Similar to My Pathway in Science and Teaching (20)
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
Geopsy yaygın olarak kullanılan profesyonel bir program. Özellikle, profesyonel program deneyimi yeni mezunlarda çok aranan bir özellik. Bir öğrencim çalışmasında kullanmayı planlıyor.
This comprehensive program covers essential aspects of performance marketing, growth strategies, and tactics, such as search engine optimization (SEO), pay-per-click (PPC) advertising, content marketing, social media marketing, and more
New Explore Careers and College Majors 2024.pdfDr. Mary Askew
Explore Careers and College Majors is a new online, interactive, self-guided career, major and college planning system.
The career system works on all devices!
For more Information, go to https://bit.ly/3SW5w8W
Exploring Career Paths in Cybersecurity for Technical CommunicatorsBen Woelk, CISSP, CPTC
Brief overview of career options in cybersecurity for technical communicators. Includes discussion of my career path, certification options, NICE and NIST resources.
24. Asperity Hazard Model Maps of recurrence interval are shown for (a) Hs = 12.5km over the region of analysis conducted by Oncel and Wyss (2000) and (b) Hs =4km . Geodetical Moment Rate Kostrov 1974 Geodetical Strain Rate Ward, 1994 Oncel and Wilson, 2006 NBF CMF
25. Coulomb stress and aftershocks: Example from western Canada Distance Along Strike Oncel, 2002 and 2007
26. Almost 1000 stations in Japanese Islands daily measurement of location with accuracy of 1[cm] GPS Earth Observation Network (GEONET)
32. Fluid effects of time-lapse seismic velocity: An experimental study Consultant: Osamu Nishizawa Exploration Geophysics Research Group, Advanced Industrial Science and Technology
33. Seismology - Rock Physics Fluid Effects of 4D Seismic Wave Propagation through Rocks Forecasting Study for Seismic Mechanism in Saudi Arabian Oil Fields Area
35. Fluid effects of time-lapse seismic velocity: An experimental study Particle velocity at the surface (Laser DopplerVibrometer) LDV Wave Memory PC 500 mV Waveform Generator Sample Fluid Container PZT Synthesizer & Amp. Optical unit of LDV reflection sheet
36. % Change Porosity Effecting Seismic Velocity Water Injection Velocity Saturatio n
Active faults in Japan digitized from the 1:200,000 active fault maps produced by the Research Group. Negative Correlations : Stress suddenly released of larger magnitude seismicity on interconnected faults of larger total surface Positive Correlations: Stress is gradually released by lower magnitude seismicity on smaller fault strands. Tohoku Events: July 26 event (M=6.2) were located in a positive correlation (Area III) noted to be anomalously quiescent. p for Active Faults of Japan (1991).
The study area was divided into three regional tectonic subdivisions consisting of a region of shear in the north associated with the Northern Anatolian Fault Zone (NAFZ), a region dominated by extension in the back-arc region of central Turkey, and a region of compression along the Aegean subduction zone. Seismotectonic parameters (D q and b) and geodetic strains (shear and dilatation) are shown in the table at right for each of the 25 seismic zones
Region of Strike-Slip: Over the full range: A significant positive correlation is observed between seismic clustering (D) and the Gutenberg-Richter b value along the NAFZ strike slip zone. Region of Extension: In this subdivision, seismic clustering (D 2 and D 15 ) correlate positively with dilatation (r = 0.67 and 0.73 with p = 0.02 and 0.01 respectively). The correlations suggest that increased rates of extension produce increasingly dispersed seismicity. Region of Compression: One would expect seismicity to correlate moreso with dilatation in a subduction zone. However, dilatation along the subduction zone is on average only slightly negative. Dilatation is positive in the areas to the northeast (17 nstrain/a) and negative (-29 nstrain/a) farther west along the subduction zone. This combination of positive and negative dilatation along the subduction zone is probably responsible for the lack of a more significant correlation between b and dilatation. The change of dilatation from positive to negative as one goes east to west along the subduction zone suggests a transition in plate interaction from transtensional to transpressive.
Region of Strike-Slip: Over the full range: A significant positive correlation is observed between seismic clustering (D) and the Gutenberg-Richter b value along the NAFZ strike slip zone. Region of Extension: In this subdivision, seismic clustering (D 2 and D 15 ) correlate positively with dilatation (r = 0.67 and 0.73 with p = 0.02 and 0.01 respectively). The correlations suggest that increased rates of extension produce increasingly dispersed seismicity. Region of Compression: One would expect seismicity to correlate moreso with dilatation in a subduction zone. However, dilatation along the subduction zone is on average only slightly negative. Dilatation is positive in the areas to the northeast (17 nstrain/a) and negative (-29 nstrain/a) farther west along the subduction zone. This combination of positive and negative dilatation along the subduction zone is probably responsible for the lack of a more significant correlation between b and dilatation. The change of dilatation from positive to negative as one goes east to west along the subduction zone suggests a transition in plate interaction from transtensional to transpressive.
North Boundary Fault μ : shear rigidity (~3×1010 N/m2), Hs: seismogenic layer’s thickness A: Surface area over which strain release is distributed.
The combined static stress changes caused by the summed effects of the October and December 1985 Nahanni earthquakes are shown in Figure 3c. I now examine if the subsequent 25 March 1988 SE Nahanni (Mw=6.2) and the 22 May 1988 NW Nahanni (Mw=5.0) events might have been triggered by the previous larger Nahanni earthquakes. ISC depths of the 1988 events are 10.18±2.63 km and 8.86 ± 4.39 km respectively but unpublished aftershock data [R.J. Wetmiller, personal comm., 2002] indicate that the depth for the March event is 6-8 km similar to the depths of the 1985 events. Also, the focal mechanisms of the March and May 1988 earthquakes are essentially the same (strike=170-165 degrees, dip=39-32 degrees). The aftershocks of the March 1988 earthquake and its estimated fault projection [based on the relation of moment-fault dimension relation, 18] are located on the map of combined static stress changes. The aftershock cluster of the March 1988 event seems to extend beyond the likely rupture plane and so occur on a plane activated by the 1985 events, and the March 1988 therefore was probably triggered by the previous events. Moreover, the May and March 1988 Nahanni events occur at opposite ends the 1985 fault ruptures and so are evidence of bilaterally activated along strike stress enhancements. Subsequent changes in seismicity (1985-2002) appear related to the pattern of co-seismic stress changes due to 1985 Nahanni earthquakes along their dipping planes with SE-NW ruptures (Figure 3b). A bilateral increase in stress loading is indicated Distance Along Strike by (i) the March and May 1988 mainshock locations, (ii) the larger post 1985 events occur to the south; (iii) the pattern of regional seismicity. The four largest post-December 85 events occur in the southern zone are, related to aftershocks of the 1985 Nahanni mainshocks and suggest unilateral rupture growth to the south [see Figure 4 of eg., Horner et al., 1990]. The March and May 1988 mainshocks, to the south and to the north of the 1985 events indicate a bilateral increase of seismic activity.Coulomb failure theory and variable slip models are used to calculate Coulomb stress changes for large earthquakes in the Nahanni region of Canada. Stress interactions between the Nahanni events are calculated through the dipping plane rather than flat plane since the stress change models are compared better to the aftershock data which are distributed along dip. Thus, in 1988 mainshocks of Mw=6.2 and Mw=5.2 occurred south and north of the 1985 rupture zone earthquakes possibly indicating an increase in the seismic hazard in the along-strike direction. In general, the zones of shadow and stress enhancement along fault dip and strike appear to govern the locations of the aftershocks. A previously proposed seismic gap or zone of quiescence in this region can be explained by a stress shadow zone. In contrast, aftershocks are clustered in the zones of stress enhancement. The pattern of subsequent 1988-2002 earthquake activity appears to be similar to the aftershock pattern and indicates that seismicity in the region continues to be affected by the stress changes due to the Nahanni events. Stress changes is computed on the E2 fault plane to understand the E1-E2 fault interaction than the analysis (see Figure 3c). Stress through the largest asperity of E2 in shallower depth has been largely observed to have increased while stress through the intermediate asperity, which is suggested to be center for earthquake epicenter, is partially appeared to have decreased, that may be a cause a delay of about two months for the onset time of December 23 event.
Oncel and Aydan - 2003
We analyzed seismicity in the region surrounding the Izmit Sapanca fault during a 7.4 yr period (1991–1998.4) preceding the 1999 Izmit event ( MD = 6.8 or Mw = 7.4). The study area lies in northwestern Turkey between 40.5◦ to 41◦ north latitude, and 29◦ and 31◦ east longitude. Seismic events during this time were subdivided into smaller overlapping time intervals for analysis and comparison. The correlation between b andDvaried from significantly positive to negative and back again during the analysis period. Oscillations in b-value have been reported by others (see Main & Meredith 1989; Henderson & Main 1992; Vinciguerra 2002). The results of this study reveal anomalous behaviour in the intermediate-termseismicity preceding the Izmit event. Phase III seismicity, approximately 1.5–3 yr preceding the event, remained clustered, and was characterized by a rapid rise in b from 1.6 to 2.26. Over the long-term (approximately 50 yr), fluctuations in b-value reached higher and higher peaks (Fig. 8). In western Turkey, b-value rose from 1.6 in 1974 to 2.1 in 1992 and then to 2.26 in 1998. We are missing the details of these variations from 1985 to 1992 and for the 1.5 yr immediately preceding rupture. A similar increase is observed in the yr leading up to the Coalinga earthquake (Henderson & Main 1992). Examination of data presented by Henderson & Main (1992) shows that oscillations in b-value reached their highest value about 3 months preceding final rupture. The b-value rose to maxima of 1.8 and 1.85 in 1973 and 1976, respectively, before rising to approximately 2.25 prior to the Coalinga event. We observe positive correlations between D and b when the bvalue is high and high negative correlation when the b-value is relatively low (Fig. 9). This suggests that in the Izmit area, as the probability of large earthquakes increases (lower b-value) there is a corresponding tendency for seismicity to become increasingly clustered. Concentration of maximum GPS strain along the rupture zone appears to be a long-term characteristic of the Izmit–Sapanca fault segment from 1988 to 1998, leading up to final rupture (see Fig. 1). This also corresponds to a time during which D remains close to or less than 1 (thus relatively clustered) and during which b increases. The final period of anomalous behaviour preceding the Izmit event (Phase III, Figs 9 and 11) is associated with accelerated low magnitude seismicity (increasing b-value) during which seismicity becomes more dispersed but remains relatively clustered with ( D <1). This behaviour is similar to the negative feedback process described by Henderson & Main (1992) in which strain release becomes increasingly dispersed while event magnitude drops. At Izmit, the results suggest that rupture occurs on faults with smaller and smaller surface area during this phase. Henderson & Main (1992) observe a period of positive feedback in which faults begin to coalesce leading to larger magnitude events.We do not observe this phenomenon; however, we suspect that the period of accelerated seismicity associated with Phase III eventually led to coalescence of fault surfaces and final rupture.We did not see the drop in b-value often reported to precede a major event. This drop, if it occurred, appears to have been fairly abrupt in the case of the 1999 Izmit event. Data presented by Henderson et al. (1992) for the Coalinga earthquake near Parkfield, California, indicate that this drop can be quite sudden, appearing only 2–3 months prior to rupture. The frequency of earthquake occurrence may not permit a statistically accurate short-term estimate of the b-value. In cases where the number of observed events preceding main rupture is too low to resolve the drop in b-value, cycles of accelerated low magnitude seismic activity in which b becomes anomalously high ( >2) may serve as an early warning of an impending large magnitude rupture. Analysis of microseismic data provided by increasingly dense seismic networks will shorten the period of analysis needed to identify statistically significant trends in seismic behaviour.
AIC: Akaike Information Criteria How to decrease Noise Value?
I had chance to contact with Osamu Nishizawa from Geological Survey of Japan to establish a create a Applied Seismology Laboratory at the Earth Sciences Department of KFUPM. Osamu Nishizawa-AIST
The sampling interval may be the sampling rate of the A/D convertor. In your experiments, sampling rate will be 20 nsec (50 MHz) or 50 nsec (20 MHz). 500 Hz is too slow for observing ultrasonic waves. Fluid The details of waveform measurements are mostly same as those described in Nishizawa et al. (1997, 1998). A single cycle 500 kHz sine wave (burst mode) is generated by a signal generator and then it is amplified to 100 V peak-to peak by a wide-band power amplifier. The high-voltage signal drives the wave source, PZT. The PZT then emits (send out) elastic waves, which propagate through the medium. The LDV uses a laser beam that is focused at the array point marked on a thin reflection sheet that is mounted on the sample surface (Fig. 1). The reflection sheet reflects most of the laser beam in the incident direction (Nishizawa et al., 1998). The incident beam direction is perpendicular to the major surface, and thus the observed waveform is the vertical component of the vibration. The output signal of LDV is fed to a wave memory (Compuscope, Gage A. S. Inc.), and the digitized signal is stored in a computer. To increase the signal-to-noise ratio of the waveform, the PZT is repeatedly driven by the same input signal and the waveforms are stacked. The stacking removes the incoherent high-frequency noise caused by the electronic circuit of the LDV. We stacked waveforms 1000 times ( in present study of Oncel 2000 times) and used the stacked waveform for analyses.
Seismic velocity changes due to increase the size of porosity is faster than the velocity changes due to lower porosity rocks.
Seismic velocity changes due to oil injection is observed higher (%30) as well as appeared higher porosity change (%50).
AIC: Akaike Information Criteria How to decrease Noise Value?