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Partitioned Waveform Inversion Applied to Eurasia and Northern Africa

Description: This report summarizes the data analysis achieved during Heather Bedle's eleven-week Technical Scholar internship at Lawrence Livermore National Labs during the early summer 2006. The work completed during this internship resulted in constraints on the crustal and upper mantle S-velocity structure in Northern Africa, the Mediterranean, the Middle East, and Europe, through the fitting of regional waveform data. This data extends current raypath coverage and will be included in a joint inversion along with data from surface wave group velocity measurements, S and P teleseismic arrival time data, and receiver function data to create an improved velocity model of the upper mantle in this region. The tectonic structure of the North African/Mediterranean/Europe/Middle Eastern study region is extremely heterogeneous. This region consists of, among others, stable cratons and platforms such as the West Africa Craton, and Baltica in Northern Europe; oceanic subduction zones throughout the Mediterranean Sea where the African and Eurasian plate collide; regions of continental collision as the Arabian Plate moves northward into the Turkish Plate; and rifting in the Red Sea, separating the Arabian and Nubian shields. With such diverse tectonic structures, many of the waveforms were difficult to fit. This is not unexpected as the waveforms are fit using an averaged structure. In many cases the raypaths encounter several tectonic features, complicating the waveform, and making it hard for the software to converge on a 1D average structure. Overall, the quality of the waveform data was average, with roughly 30% of the waveforms being discarded due to excessive noise that interfered with the frequency ranges of interest. An inversion for the 3D S-velocity structure of this region was also performed following the methodology of Partitioned Waveform Inversion (Nolet, 1990; Van der Lee and Nolet, 1997). The addition of the newly fit waveforms drastically extends the range of ...
Date: July 27, 2006
Creator: Bedle, H.; Matzel, E. & Flanagan, M.
Partner: UNT Libraries Government Documents Department

A Variable-resolution Surface Wave Dispersion Study of Eurasia, North Africa, and Surrounding Regions

Description: This paper presents the results of a large-scale study of surface wave dispersion performed across Eurasia and North Africa. Improvements were made to previous surface wave work by enlarging the study region, increasing path density, improving spatial resolution, and expanding the period range. This study expands the coverage area northwards and eastwards relative to a previous dispersion analysis, which covered only North Africa and the Middle East. We have significantly increased the number of seismograms examined and group velocity measurements made. We have now made good quality dispersion measurements for about 30,000 Rayleigh wave and 20,000 Love wave paths, and have incorporated measurements from several other researchers into the study. A conjugate gradient method was employed for the group velocity tomography, which improved the inversion from the previous study by adopting a variable smoothness. This technique allows us to go to higher resolution where the data allow without producing artifacts. The current results include both Love and Rayleigh wave inversions across the region for periods from 7 to 100 seconds at 1{sup o} resolution. Short period group velocities are sensitive to slow velocities associated with large sedimentary features such as the Caspian Sea, West Siberian Platform, Mediterranean Sea, Bay of Bengal, Tarim Basin, and Persian Gulf. Intermediate periods are sensitive to differences in crustal thickness, such as those between oceanic and continental crust or along orogenic zones and continental plateaus. At longer periods, fast velocities are consistently found beneath cratons while slow upper mantle velocities occur along rift systems, subduction zones, and collision zones such as the Tethys Belt. We have compared the group velocities at various periods with features such as sediment thickness, topographic height, crustal thickness, proximity to plate boundaries, lithospheric age and lithospheric thickness, and find significant correlations. We don't find any similar correlation between the longest ...
Date: March 21, 2005
Creator: Pasyanos, M E
Partner: UNT Libraries Government Documents Department

Preliminary maps of crustal thickness and regional seismic phases for the Middle East and North Africa

Description: As part of the development of regional seismic discrimination methods for the Middle East and North Africa (MENA) the author is building a database of information related to seismic propagation and crustal structure as well as associated geologic-tectonic and geophysical data. He hopes to use these data to construct and test models of regional seismic propagation and evaluate various detection/discrimination scenarios. To date, the database has been developed by building on a list of references for MENA provided by the Institute for the Study of the Continents (INSTOC) at Cornell University. To this list the author has added an equal number of references resulting from his own literature search which has emphasized papers dealing with seismicity and regional and teleseismic phase data. This paper represents an initial attempt to consolidate some of the information from the database into a form useful to researchers modeling regional seismic waveforms. The information compiled in this report is supplemental to the INSTOC database and has not been compiled anywhere else. What follows is a series of maps which illustrate the spatial variation of seismic phase velocities and crustal thickness. The text identifies the sources of information used in the map preparation. Data for the compilation of these maps has come from an initial search of the database as it presently exists and is not intended to be exhaustive. The author hopes that this initial exercise will help to identify areas and types of data that are deficient and help to focus future data gathering activities.
Date: September 6, 1995
Creator: Sweeney, J.J.
Partner: UNT Libraries Government Documents Department

Status report of propagation models: Middle East and North Africa (S5.3)

Description: An improved understanding of the influence that tectonic structure has on regional seismic phases is needed to improve the current performance of regional discriminants and their transportability to the Middle East and North Africa. In the case that the crustal structure can be approximated by a flat layered laterally invariant medium, layer-cake reflectivity modeling can be used to obtain an accurate representation of regional phases. However, a laterally heterogeneous crust is just as common as a layered cake structure and in this case large variations in regional phase amplitudes are not uncommon. For instance, it has been shown that rough surface topography and undulations in the Moho can cause the transfer of energy between various surface wave modes and between surface waves and body waves greatly increasing the potential variability of seismic phases. Larger scale structure such as thickening or thinning of the crust can also greatly affect phase propagation. In some instances, changes between different tectonic regions such as that which occurs at a continental-oceanic boundary can completely block phases such as Lg rendering certain discriminants useless. In addition to structure along the path, lateral structure and free surface topography near the source and receiver can cause complex scattering effects with strong directional, frequency, and near-field effects. Given that the Middle East and North Africa cross many different tectonic boundaries, the authors are using numerical propagation models to understand how the relevant tectonic features affect the propagation of primary discriminant phases.
Date: November 1, 1995
Creator: Schultz, C.A.; Patton, H.J. & Goldstein, P.
Partner: UNT Libraries Government Documents Department

Comparison of gridded versus observation data to initialize ARAC dispersion models for the Algeciras, Spain steel mill CS-137 release

Description: On May 30, 1998 scrap metal containing radioactive Cesium-137 (Cs-137) was accidentally melted in a furnace at the Acerinox steel mill in Algeciras, Spain. Cs-137 was released from the mill's smokestack, and spread across the western Mediterranean Sea to France and Italy and beyond. The first indication of the release was radiation levels up to 1000 times background reported by Swiss, French, and Italian authorities during the following two weeks. Initially no elevated radiation levels were detected over Spain. A release of hazardous material to the atmosphere is the type of situation the Atmospheric Release Advisory Capability (ARAC) emergency response organization was designed to address. The amount and exact time of the release were unknown, though the incident was thought to have taken place during the last week in May. Using air concentration measurements supplied by colleagues of ARAC in Spain, France, Switzerland, Italy, Sweden, Russia and the European Union, ARAC meteorologists estimated the magnitude and timing of the release (Vogt, 1999). Correctly locating the downwind footprint is the most important goal of emergency response modeling. In this study, we compare predicted results for the Algeciras event based on four wind data sources: (1) US Navy Operational Global Atmospheric Prediction System (NOGAPS) data alone, (2) surface and upper air observations alone, (3) NOGAPS data together with surface and upper air observations, and (4) forecasts from ARAC's in-house execution of the U.S. Navy Operational Regional Atmospheric Prediction System (NORAPS) (without surface or upper air observations). We compare the resulting dispersion predictions from ARAC's diagnostic dispersion modeling system to the measurements supplied by our European colleagues to determine which data source produced the best results.
Date: May 28, 1999
Creator: Aluzzi, F J; Pace, J C; Pobanz, B M & Vogt, P J
Partner: UNT Libraries Government Documents Department

High Energy Neutrinos with a Mediterranean Neutrino Telescope

Description: The high energy neutrino detection by a km{sup 3} Neutrino Telescope placed in the Mediterranean sea provides a unique tool to both determine the diffuse astrophysical neutrino flux and the neutrino nucleon cross section in the extreme kinematical region, which could unveil the presence of new physics. Here is performed a brief analysis of possible NEMO site performances.
Date: September 1, 2007
Creator: Borriello, E.; /Naples U. /INFN, Naples /Valencia U., IFIC; Cuoco, A.; U., /Aarhus; Mangano, G.; /Naples U. /INFN, Naples et al.
Partner: UNT Libraries Government Documents Department

Capital Ships, Commerce, and Coalition: British Strategy in the Mediterranean Theater, 1793

Description: In 1793, Great Britain embarked on a war against Revolutionary France to reestablish a balance of power in Europe. Traditional assessments among historians consider British war planning at the ministerial level during the First Coalition to be incompetent and haphazard. This work reassesses decision making of the leading strategists in the British Cabinet in the development of a theater in the Mediterranean by examining political, diplomatic, and military influences. William Pitt the Younger and his controlling ministers pursued a conservative strategy in the Mediterranean, reliant on Allies in the region to contain French armies and ideas inside the Alps and the Pyrenees. Dependent on British naval power, the Cabinet sought to weaken the French war effort by targeting trade in the region. Throughout the first half of 1793, the British government remained fixed on this conservative, traditional approach to France. However, with the fall of Toulon in August of 1793, decisions made by Admiral Samuel Hood in command of forces in the Mediterranean radicalized British policy towards the Revolution while undermining the construct of the Coalition. The inconsistencies in strategic thought political decisions created stagnation, wasting the opportunities gained by the Counter-revolutionary movements in southern France. As a result, reinvigorated French forces defeated Allied forces in detail in the fall of 1793.
Date: August 2014
Creator: Baker, William C.
Partner: UNT Libraries

Newsmap. Monday, August 9, 1943 : week of July 29 to August 5, 204th week of the war, 86th week of U.S. participation

Description: Front: Text describes action on various war fronts: Italy, Sicily, Rumania, Russia, Germany, Burma-China, Southwest Pacific. Map: Strategic air distances across the Mediterranean./ Relief shown by hachures. Photographs: Army engineers work in the Aluetians; A Tommy reads "Soldier's guide to Sicily"; Royal Artillery Detachment stationed north of Syracuse, Sicily examines damage done by Italians to a mobile anti-aircraft train; Nazis surrender to U.S. Infantrymen near Carlentini; Junkers-290 transport shot down by an RAF Marauder near the coast of Bastia, Corsica; U.S. Marines push a generator into position near Munda; Japanese interpreters of the U.S. Army decipher papers found on a wounded Japanese officer; A winch pulls a mud-splattered jeep free on Rendova; 155mm rifle sends rounds into Munda from Rendova Island. Back: [text and ill.]: The long, tough fight ahead : beyond sunny Italy!/ Back text includes quote from the President of the United States, July 28, 1943: "I confess that I myself am sometimes bewildered by conflicting statements that I see in the press ..."
Date: August 9, 1943
Creator: [United States.] Army Orientation Course
Partner: UNT Libraries Government Documents Department

Relocation of Gulf of Aqaba earthquakes using the JSOP Bulletin

Description: Ground truth information (i.e. precise information about the hypocenter and origin time of aseismic event) is difficult to obtain in the Middle East and North Africa region. One source of ground truth we are attempting to exploit is data from local seismic networks. An electronic bulletin from the second phase of the Joint Seismic Observation Period (JSOP), with participating countries in the eastern Mediterranean region, provides a source of local network data not ordinarily available. I have used JSOP bulletin data for the period January 1996 through June 1996 to relocate over 100 earthquakes occurring in and around the Gulf of Aqaba. Fourteen of these earthquakes have picks in the bulletin for stations surrounding the Gulf (Egypt Saudi Arabia, Israel,and Jordan). The rest of the data involves picks for stations either in Israel, Jordan, and Saudi Arabia (east side and north of the Gulf) or for stations in Israel, Jordan, and Egypt (west side and north of the Gulf). The VELEST code (Joint Hypocenter Determination method) was used to calculate improved locations (over what can be obtained from single event determinations--SED with poor station configurations) for the all the earthquakes in the data set. Location differences between the JHD solution and SED are discussed, along with determination of the minimum 1-Velocity model. Waveform correlation was used to validate observed event clusters in the VELEST solutions. This provided evidence that some of the VELEST solutions are more accurate than NEIC solutions. The subset of 14 events with good station coverage provides a good set of ground truth (location uncertainty {lt}5 km). The rest of the events are probably located more accurately with local data than is available from NEIC determinations, but such a conclusion needs to be supported by further study.
Date: July 3, 1997
Creator: Sweeney, J.J.
Partner: UNT Libraries Government Documents Department