Seismic Resolution The definition of the term thin bed involves the concept of the resolving power (Widess, 1973) thus seismics is impacted by resolution. Most geological structures have a smaller vertical dimension than a horizontal one (Chang et al, 1996), thus, the ratio of the vertical dimensions plays a very important role in seismic resolution. As the dimension ratio decreases, the difficulty in identifying geological events increases and become more challenging (Chang et al, 1916). Sheriff, (1991) defines Seismic resolution as the ability to separate two features that are very close together; the minimum separation of the bodies before their identifies are lost. It is seen as the minimum distance between two events that can be seen …show more content…
Seismic vertical resolution relates how for apart two interface must be to distinguish separate reflections from them. It can also be defined to be how thick a bed must be to allow distinguishable reflection from the bed’s top and bottom, thus two vertically seismic features can be resolved separately (Paola et al, 2011). Based on the analysis of the amplitude tuning effect in a single bed reflection, Widess (1971) defines vertical resolution as one quarter of the seismic wavelength, where the bed thickness is less than one quarter of the seismic wavelength. Below tuning thickness (ʎ/4) individual beds will not be resolved. Vertical resolution can be enhanced by higher frequencies, high bandwidth and reduced wavelength (Sheriff, 1991). Vertical resolution decreases with depth because higher frequencies are attenuated with depth. The deconvolation operation improves vertical …show more content…
Widess in his work, consider a bed to be a ‘thin’ bed when the thickness is about 1/8, one - eighth of the predominant wavelength, computed using the velocity of the bed. A bed is thin at about ʎ/8 where a complex waveform across it does not differ significantly from the derivative of the convolving wavelet itself. Its’ composite waveform stabilizes. The apparent thickness is actually put at ʎ/4.6 which is the peak – to – trough time of the derivative of a Ricker wavelet (Kallweit and Wood, 1982). Rayleigh criterion of peak – to – trough separation at one – quarter wavelength (ʎ/4) is more workable and a more widely accepted definition of resolution limit (Kallweit and Wood,
Marshak, S. (2009) Essentials of Geology, 3rd ed. New York: W.W. Norton & Company, ch. 11, p. 298-320.
Van Siclen, D. "The Houston Fault problem." Institute of Professional Geologists. Ed. 3rd Annual Meeting. Texas, 1967. p.9-31.
Earthquakes play a major role into understanding the composition and materials that exist within the Earth (Merali and Skinner, 2009, p.252). Earthquakes are the main source of insight into the inner workings of the earth, due to the nature of the seismic waves they produce. P and S waves are reflected and refracted at different boundaries within the earth, and this enables seismologists to make inferences about the internal composition and structural of planet Earth. (Merali and Skinner, 2009, p.252).
Earthquakes are a natural part of the Earth’s evolution. Scientific evidence leads many geologists to believe that all of the land on Earth was at one point in time connected. Because of plate tectonic movements or earthquakes, continental drift occurred separating the one massive piece of land in to the seven major continents today. Further evidence supports this theory, starting with the Mid-Atlantic ridge, a large mass of plate tectonics, which are increasing the size of the Atlantic Ocean while shrinking the Pacific. Some scientists believe that the major plate moveme...
Healy, J. H., Rubey, W. W., Griggs, D. T., & Raleigh, C. B. (1968, September). The Denver Earthquakes. Science, 161(3848), 1301-1310. Retrieved from JSTOR database.
7. Refer to Figure 22-6. What name is given to the core of the modern-day North American continent that formed in the Proterozoic?
From studying the science behind the San Francisco earthquake, scientists have made a number of important discoveries involving how earthquakes function. At 5:12 on a fateful April morning in 1906, the mammoth Pacific and North American plates sheared each other at an incredible twenty-one feet along the San Andreas fault, surpassing the annual average of two inches (“San Francisco Earthquake of 1906”) (“The Great 1906 Earthquake and Fires”). A few seconds later, the destructive earthquake occurred. The ground shifted at almost five feet per second, and the shaking could be felt all the way from southern Oregon to southern Los Angeles to central Nevada (“Quick”) (“The Great 1906 San Francisco Earthquake”). In fact, the earthquake could be registered in a seismograph on Capetown, South Africa, an astounding 10,236 miles away...
Before examining the Northridge event, understanding the naturally occurring hazard that is an earthquake will help to better understand exactly what happened and why it was such an important geological event. With four distinct layers, two layers, the crust and upper portion of the mantle, compose the skin that is the surface layer of the Earth. The crust is not a single, continuous piece. It is actually several different pieces, or plates, that come together to form the puzzle that comprises the surface of the Earth. These plates are in constant motion rubbing against one another. These areas, known as fault lines, where the plates rub up against one another have spots where one plate ”gets stuck while the rest of the plate keeps moving. When the plate has moved far enough, the edges unstick and is how most of the earthquakes around the world occur” (Wald, 2012). The energy stored from the friction of the two plate...
remains in highest regards among seismologists, engineers and geologists. It is said to be a
Source 6. A diagram of how a seismograph works and the measurements Source 7. Statistics on the Earth’s earthquakes
Psychology is the study of the mind and the behavior of mammals. Geology is a science that deals with the history of the earth and its life, recorded in rocks. The earth is consistently moving its tectonic plates. Therefore, there may be over 100 earthquakes a day; most of these earthquakes go unnoticed by humans on the crust of the earth. Other earthquakes for example, the one in 2011 located in Japan and the Loma Prieta earthquake of 1989 (Earth- Marshak). Unfortunately, many people died in horrific ways during these deadly earthquakes, leaving thousands diagnosed with psychological disorders such as, Posttraumatic Stress Disorder and Specific Phobias directly related to the natural environment of the earth.
The historical use of GNSS in Offshore surveying was initially limited to x and y components meaning there was no z axis rendering 3D visualisation impossible in early years of this partnership. This was due to the capabilities of the receivers, which were land based at the time, not being able to comprehend data in three dimensions. This resulted in less accurate results due to the component of height (z) not being taken into account. This would have meant numerous problems for offshore surveyors in the early years of GNSS being used. But as time passed the capabilities of the land based receivers improved resulting into the component of z being taken into account. This resulted in more accurate results, so much so that it became a common requirement for all receivers when undertaking this task. As ...
Fig. 1 shows the map of a part of Asia in which the stars indicate the location of earthquakes and solid circle indicates the location of observing station Agra (27.2o N, 78o E). The details of these earthquakes are mentioned in table 1 which shows the days of occurrence, magnitudes, depths (km), locations (Latitude and Longitude in degrees), radius of influence zone (km) and distances from the Agra station (km). The radius of influence zone is calculated by using the expression R = 100.43M, where M is the magnitude of the earthquake [21]. Although these earthquakes have occurred far away from the observing station Agra, atleast two of them are well covered (> 1000 km) by the radius of the influence zone. The details of the earthquake data have been taken from United States Geological Survey (USGS) website www.earthquake.usgs.gov.in. We have also seen the variations of geomagnetic parameters such as Dst index and ∑ Kp index for each case separately and data have been taken from National Aeronautics and Space Administration (NASA) website http://omniweb.gsfc.nasa.gov/form/dx1.html. We can see from table 1 that all the earthquakes have shallow depths except one of them (46 km), but we cannot ignore this earthquake because of its relatively large magnitude (M = 7.8). Further, it may be seen from the table 1 that two of the earthquakes occurred in the month of April, one in July, and rest two in September, 2013.
Earthquakes belong to the class of most disastrous natural hazards. They result in unexpected and tremendous earth movements. These movements results from dissemination of an enormous amount of intense energy in form of seismic waves which are detected by use of seismograms. The impact of earthquakes leaves behind several landmarks including: destruction of property, extensive disruption of services like sewer and water lines, loss of life, and causes instability in both economic and social components of the affected nation (Webcache 2).
The main definition of natural disaster is “any catastrophic event that is caused by nature or the natural processes of the earth”. Natural disasters happen all around the world, it is a major event resulting from a natural process of the Earth, for example the most common are hurricanes, earthquakes, tsunamis, tornados, and volcanic eruptions. A natural disaster can cause a lot of damage, and also loss of life. These disasters typically cause economic damage, which it´s very difficult to recover from. Some of the events will not rise to the level of a natural disaster if it occurs in an area without vulnerable population, however if it occurs in a vulnerable and populated area, it is considered a natural disaster, and it can cause serious