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Encyclopedia: Seismic wave   (Site not responding. Last check: 2007-11-07) A seismic wave is a wave that travels through the Earth, often as the result of an earthquake or explosion. Seismic waves are studied by seismologists, and measured by a seismograph or seismometer. A quick way to determine the distance from a location to the origin of a seismic wave is to take the difference of arrival time from the P wave to the S wave in seconds and multiply by 8 kilometers per second. www.nationmaster.com /encyclopedia/Seismic-wave   (1146 words)

Seismic tomography - Open Encyclopedia   (Site not responding. Last check: 2007-11-07) Seismic tomography uses digital seismographic records to image the interior of the Earth. These earthquakes are them considered to "illuminate" the interior of the earth with seismic waves. The time that the waves arrive at seismic stations can then be used to calculate the waves' speed through the Earth. open-encyclopedia.com /Seismic_tomography   (135 words)

Artemis Project: Lunar Seismic Actvity The largest recorded seismic activities are approximately equivalent to a 4 on the richter scale, with 1-2 being typical. The lunar seismic activity is usually caused from tidal forces and secondary effects from impacts. Although the effect of lunar seismic activity is widespread, a lunar astronaut would hardly notice a moonquake happening, and precautions for moonquakes are probably unnecessatry. www.asi.org /adb/m/03/07/seismic-activity.html   (363 words)

Seismic wave -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-11-07) Seismic waves are studied by (A scientist who studies earthquakes) seismologists, and measured by a (A measuring instrument for detecting and measuring the intensity and direction and duration of movements of the ground (as an earthquake)) seismograph or (Click link for more info and facts about seismometer) seismometer. Because of their low frequency, they are more likely than body waves to stimulate (An excited state of a stable particle causing a sharp maximum in the probability of absorption of electromagnetic radiation) resonance in buildings, and are therefore the most destructive type of seismic wave. An excellent audience demonstration for seismic waves is shown in (Click link for more info and facts about slinky seismology) slinky seismology. www.absoluteastronomy.com /encyclopedia/s/se/seismic_wave.htm   (559 words)

SEISMIC DATA INVERSION   (Site not responding. Last check: 2007-11-07) The seismic inversion is excellent at deriving impedance contrasts across layered interfaces within the seismic reflection data, which reveals short-scale (tens of meters) variations of impedance; however, it is not able to determine the large-scale (hundreds of meters) vertical trends. Seismic impedance is difficult to use to infer lateral variations in physical properties directly related to compaction and dewatering processes, so estimates of seismic impedance were converted to porosity using an empirical relationship between impedance and porosity as described below. Figure F3 is a plot of the seismic impedance vs. porosity for upper and lower Shikoku Basin facies sediment as estimated from wireline logging velocities, LWD density, and core porosity. www-odp.tamu.edu /publications/190196SR/354/354_5.htm   (521 words)

What Is Seismology and What Are Seismic Waves?   (Site not responding. Last check: 2007-11-07) Seismology is the study of earthquakes and seismic waves that move through and around the earth. Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. There are several different kinds of seismic waves, and they all move in different ways. www.geo.mtu.edu /UPSeis/waves.html   (492 words)

SEISMIC STRATIGRAPHY Seismic Unit I (0-46.7 mbsf) is acoustically semitransparent with some low-amplitude reflectors toward the base of the unit that onlap the irregularities of acoustic basement (Fig. Seismic Unit I has a drape geometry, indicated by uniform thickness of the unit in the central part of the basin and a bottom morphology that follows the irregularities of acoustic basement (Fig. The overall onlapping fill character of the seismic units drilled in the Palmer Deep basins suggests that the style of sedimentation was dominated by hemipelagic drape and by infilling of the basins with sediment gravity flows, probably from a local source. www-odp.tamu.edu /publications/178_IR/chap_07/ch7_ht11.htm   (1846 words)

Report On Seismic Activity Due To The Aircraft Impact At The Pentagon. Possible seismic signals from the airplane crash into the Pentagon may be very weak, but examination of seismic data recorded across network of three stations would help identify the signals. Hence,the seismic phase Pg (P waves propagating through Earth's crust) would propagate with nearly constant speed of about 6 km/s over the record section, where as the phase Pn (critically refracted P waves propagating through top of the uppermost mantle) propagates with an apparent speed of about 8 km/s. Although, seismic signals across the network are not as strong and clear as the WTC case (see Kim et al., 2001), three component records at station SSPA (Δ = 107.6 km) shown in Figure 6 are quite clear. guardian.150m.com /wtc/seismic/small/WTC_PENT_KIM.htm   (1906 words)

RIGZONE - Tough Times for the Seismic Data Acquisition Industry Meanwhile operators are pressuring seismic companies to assume greater risks in insurance—in some cases including liability that exceeds the annual revenue of the firm conducting the survey. As seismic acquisition changes from a precursor for exploration into an integral part of the production cycle, it brings seismic boats closer to existing drilling and production platforms, and operators want seismic contractors to indemnify the operator against incidents such as hydrocarbon spills that have little to do with mapping the earth's crust. Meanwhile, the seismic industry is in the midst of structural changes as new computing power, computer modeling, and improvements in drilling and production bring about a convergence of trends that can best be described as the virtual oilfield. www.rigzone.com /news/article.asp?a_id=5355   (1337 words)

World Oil: Integrating seismic facies and petro-acoustic modeling   (Site not responding. Last check: 2007-11-07) Seismic facies maps were used to characterize and analyze channel sands. Seismic responses ("trace shapes") at the two exploratory wells were then integrated into petro-acoustic models for calibration purposes. If Frio reservoirs have a seismic signature (in both shape and amplitude) that can be modeled from well curves, then the seismic-facies maps could be calibrated to sand thickness and/or petrophysical properties such as porosity or fluid content. www.findarticles.com /p/articles/mi_m3159/is_6_220/ai_54989086   (1337 words)

Seismic I.Q. - How to Get your House's Seismic I.Q. Seismic I.Q. is not affiliated with insurance firms or seismic retrofitting contractors and they safeguard the confidentiality of your assessments. Seismic I.Q.’s President, R.F. Chmaytelli, with over 15 years of experience in risk management for the real estate markets has reviewed as many as 1,500 projects nationwide ranging from small residential developments to large-scale commercial and industrial facilities. Seismic I.Q. has the ability to help its clients meet their real estate risk management objectives by having experienced principals familiar with the construction systems and methods used on residential properties get involved with all projects from inception to the final report and follow-ups. seismiciq.com /about.html   (436 words)

The University of Melbourne - 625-304 Applied Geophysics - Seismic Seismic exploration is the conduit for most expenditure in geophysical exploration by a wide margin. This is a response to the recognition of the highly effective way seismic data images the geometry of subsurface rocks, especially in sedimentary provinces, over almost all scales and in most environments on and off shore. Processing of seismic data enables the recognition of even details of past depositional environments from the features preserved as differences in the elastic properties of rocks. www.earthsci.unimelb.edu.au /Thomas/lt304/es304seis.html   (949 words)

Hasbrouck Geophysics, Inc.:  Excavation/Rippability (Refraction Seismic) The 48-channel seismic data were acquired with a signal-enhancement seismograph, geophone intervals of 5 feet, and an 8-pound sledgehammer source with impacts made at various distances offset and along the seismic profile. For each source point the stacked data were recorded into the same seismic data file, or record, and theoretically the seismic signal arrived at the same time from each refracting layer and thus was enhanced while noise was random and tended to be reduced or canceled. Note that the thickness of the caliche layer is estimated at approximately 12 feet since it was not possible to determine its actual thickness with the refraction seismic method because of a velocity inversion. www.hasgeo.com /refrac2.htm   (719 words)

USGS CMG "Seismic" Definition seismic reflection profile data typically acquired with a large multiple airgun array; 10 to 100 Hz spectral content (2 ms sample) and 8 to 20 sec record length; CDP interval typically 25 to 100 meters; 12 to 48 fold. seismic reflection profile data typically acquired with a single small airgun, GI gun or watergun; 50 to 500 Hz spectral content (0.5 ms sample) and 1 to 2 sec record length; CDP interval typically 3 to 5 meters; 6 to 24 fold. seismic reflection profile data typically acquired with a small sparker (2 kJ), small airgun, GI gun, or watergun; often includes two-channel data, which are independent receivers; spectral content 100 to 1000 Hz (0.25 to 0.5 ms sample); shot interval 3 to 10 meters. walrus.wr.usgs.gov /infobank/programs/html/definition/seis.html   (861 words)

Solutions From the Field - Seismic Imaging of Structural, Stratigraphic and Diagenetic Plays   (Site not responding. Last check: 2007-11-07) Seismic processing and interpretation is extensively used by the majors and larger independents, but is often considered beyond the means of smaller independents. Seismic processing follows both normal moveout (NMO) to correct effects of separation between the receiver and the source on the arrival time of reflections and dip moveout (DMO), which corrects the difference in the arrival times or travel times of reflected waves from two offset locations, and accounts for dipping reflections. Several classification schemes for seismic attributes issues were discussed: pre-stack vs. post stack, derived from data or interpretations, derived from complex trace or other interpretations, derived on a sample-by-sample basis or does the attribute represent a single interval property. www.pttc.org /solutions/sol_2003/522.htm   (1687 words)

Idaho National Laboratory - Geosciences Research - Earthquake Activity INL seismic stations record about 2000 earthquakes a year in southeast Idaho with the exception of years when earthquake swarms or large magnitude earthquakes with aftershocks occur. The passage of seismic waves through alternating layers of hard basalt and loosely consolidated (soft) sediments scatter and dampen seismic energy, resulting in earthquake ground motions which are 15-25% lower than they would be for uniform basalt rock. Several INL seismic stations are located near or within identified volcanic rift zones to provide early warning in the event of potential volcanic eruption. www.inel.gov /env-energyscience/seismic/quakes.shtml   (1158 words)

Earthquake Protection and Seismic Damage Prevention Technology from Seismic Shock Control Systems, Inc. Seismic Shock Control Systems, Inc. has developed an entirely unique product that it believes will revolutionize the manner in which structures are built and retrofitted to protect against damage sustained in the event of a major earthquake. The Seismic Shock Control Units provide a new cost-effective method by which structures are stabilized in the event of an earthquake. Seismic Shock Control Systems introduces a superior earthquake protection device that isolates up to 30% - 70% of destructive seismic motion subjected to buildings, bridges, freeways and other major structures. www.seismicshock.com   (478 words)

[No title]   (Site not responding. Last check: 2007-11-07) In other words, seismic is no longer only for explorationists hunting for new discoveries, traps and hydrocarbons. In short, reservoir quality seismic is expanding the data's scope to every phase of a project to reduce risk and uncertainty. A major problem with 4-D seismic in the past was the repeatability of the seismic surveys. www.aapg.org /explorer/2004/03mar/seismic_targets.cfm   (660 words)

Seismic   (Site not responding. Last check: 2007-11-07) Seismic is San Francisco's new epicenter for the Breaks Community. The simple goal of Seismic is to create a means of bringing the Breaks crews of the Bay Area together, to foster coordination, nurture support, further promote and ultimately create a strong, vital, and cohesive San Francisco breaks community that will continue to grow and attract international attention. Seismic is a inclusive endeavor and wishes to invite anyone who is active in the Breaks movement to contact us and tell us how they wish to get involved. seismicsf.org /about   (125 words)

Seismic Waves Given a sensitive enough detector, it is possible to record the seismic waves from even minor events occurring anywhere in the world at any other location on the globe. Locating the source of any earthquake is important, of course, in assessing the damage that the event may have caused, and in relating the earthquake to its geologic setting. Given a single seismic station, the seismogram records will yield a measurement of the S-P time, and thus the distance between the station and the event. www.seismo.unr.edu /ftp/pub/louie/class/100/seismic-waves.html   (1064 words)

Seismic Design and Construction The use of R greater than 3 in the calculation of the seismic base shear requires the use of a seismically detailed system that is compatible with R even if wind forces control. Oregon State Library Seismic Upgrade -- Today, renovation of existing historic buildings often requires construction methods to be less intrusive and construction materials to be smaller, thinner, and more manageable in order to minimize any damage to the structure’s appearance. Seismic Analysis Options For Steel Truss Bridges -- Seismic retrofitting is becoming increasingly common during major rehabilitation contracts. www.engr.psu.edu /ae/steelstuff/seismic.htm   (1128 words)

Passive Seismic? 04:2003 EXPLORER   (Site not responding. Last check: 2007-11-07) Passive seismic monitoring at Ekofisk is taking place today, with the sensor hooked up to the power and telemetry distribution system in the cable to deliver data in real time back to the client's office. Passive seismic technology clearly is gaining a foothold in both exploration and production, but the jury is still out regarding its potential real value as an exploration tool. Natural seismic sources have the drawback of sporadic distribution in time and space, and monitoring these sources may take an unpredictable amount of time to record sufficient data to construct an image that is as good as conventional seismic, according to Ridyard. www.aapg.org /explorer/2003/04apr/passiveseismic.cfm   (1787 words)

3D Seismic   (Site not responding. Last check: 2007-11-07) WE PROPOSE to shoot a 3D seismic survey which would extend and merge with the 20 square miles of 3D seismic data we have already acquired in our area of operations. We have reprocessed the seismic field data with improved statics and reinterpreted it with recalculated velocities using isochron mapping from WELL CONTROL to derive depth. Now high definition SEISMIC shows it was drilled away and downdip from the pinnacle of a feature, as were several wells on the lease. www.georgedreher.com /3D_Seismic.html   (639 words)

PUB-3000 Chapter 23 | SEISMIC SAFETY | REV'D 11/04 Being aware of state-of-the-art developments in the seismic response of structures, and using this knowledge in the performance of its functions. When moving into or rearranging work areas, each division is responsible for providing anchorage for seismic resistance of nonstructural building elements (such as research equipment and systems and related vents, plumbing, ducting, electrical wiring and equipment, fixtures, furnishings, and material storage facilities). When limited horizontal motion of the structure with respect to the floor is permitted during a seismic disturbance, the structure construction must ensure that escape routes for personnel remain open. www.lbl.gov /ehs/pub3000/CH23.html   (4293 words)

Guide to International Seismic Codes: Multidisciplinary Center for Earthquake Engineering (MCEER)   (Site not responding. Last check: 2007-11-07) Part II provides an introduction to the seismicity and pertinent geological background for the 34 countries that are included, a simplified account of the seismic code for the respective country, as well as a summary of the main developments in seismic code activity for each country. This volume summarizes probabilistic seismic hazard assessment as it is practiced in seismically active countries throughout the world. "Seismic zone tabulation -United States," (table 3-1) and a seismic zone map for the United States (figure 3-1) reprinted from the 1991 UBC are also included. mceer.buffalo.edu /infoService/bibs/intcodesPrn.asp   (980 words)

BBC News | SCI/TECH | Collapsing towers caused seismic shock The seismic signals generated by the collapsing north and south towers were much stronger than those from the two airliner impacts. The Palisades recordings of the twin tower collapses were comparable in size to the signals from a small earthquake of magnitude 2.4 that was felt on the east side of Manhattan and in the western parts of Queens earlier this year, on 17 January. However, the seismic signals from the five events on 11 September differed from a small earthquake in significant ways. news.bbc.co.uk /hi/english/sci/tech/newsid_1554000/1554560.stm   (300 words)

CVO Website - Monitoring - Real-Time Seismic-Amplitute (RSAM) System These techniques for characterizing a volcano's changing seismicity in real time (as it is occurring) rely on the amplitudes and frequencies of seismic signals rather than on the locations and magnitudes of the earthquakes. This type of seismic data is available in real time, and permits seismologists to detect and evaluate a change in the type of earthquake activity occurring beneath an active, restless volcano. Because seismicity is one of the main tools used to monitor volcanoes, CVO and UW maintain a network of 18 seismic stations within 16 kilometers of Mount St. Helens, including three stations in the crater. vulcan.wr.usgs.gov /Monitoring/Descriptions/description_RSAM_SSAM.html   (1255 words)

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