Download or read book Crustal Structure of the Iran Region from In Country and Ground Truth Data written by and published by . This book was released on 2008 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: We are investigating the crustal and upper mantle structure of the Iran region using in-country data sets of seismic phase arrival times, supplemented by ground-truth data sets developed from our previous research efforts. Other data sets from global, regional, and national bulletins in the region are being integrated as well. The in-country data sets, covering approximately the last 10 years of seismicity in the region, are being carefully reviewed for quality control, selectively re-picked, and combined with ground truth and other data sets for careful relocation of all seismic sources with magnitudes of approximately 2.5 and larger. Using these relocated sources with well-characterized uncertainties and the associated phase readings for crustal and regional phases, we perform forward modeling and tomographic inversion, under the assumption of isotropic velocities, to study the velocity structure and variability of the crust and upper mantle in this region. The resulting models and datasets will provide a well-characterized baseline for more detailed studies in the future. We are continuing efforts to discover and develop new ground truth data sets in this region. We present some of the currently available data sets for this effort, along with preliminary tomographic inversion results based on them. We present a strategy for tomography based on ray-tracing in a region for which substantial variations in crustal thickness are expected, and using datasets that have different characteristics than those normally employed for this type of study. Through relative event relocation, clusters of events have very strong constraints on relative location, depth, and origin time. For each cluster, then, there will be only a single set of free parameters addressing uncertainty in location, depth, and origin time of the cluster's hypocentroid, rather than independent parameters for each event in the cluster.
Download or read book Crustal Structure from In Country and Ground Truth Data written by and published by . This book was released on 2009 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: We are investigating the crustal and upper mantle structure of the region in central Asia bounded approximately by longitude 41-67 deg E and latitude 20-44 deg N by using in-country datasets of seismic phase arrival times, supplemented by ground truth datasets developed from our previous research efforts. We present the results of Pn tomography using a dataset consisting entirely of GT5 events in the region. From 27 calibrated earthquake clusters we extract 832 events that qualify as ground truth (GT)5 at the 90% confidence level. The raypaths of Pn readings from these events provide good coverage of most of the region except for the Makran region in the southeast. To determine an appropriate reference model for the region we compared empirical travel times calculated from the GT5 dataset to those predicted by several models: the ak135 global model (Kennett et al., 1995), the CUB2.0 model (Ritzwoller et al., 2003), and the so-called "Unified" model a 3-D velocity model of the crust and upper mantle in Eurasia, constructed from models developed by researchers at Lawrence Livermore National Laboratory (LLNL) and Los Alamos National Laboratory (LANL) (Pasyanos et al, 2004; Begnaud et al., 2004; Steck et al., 2004; Flanagan et al., 2007). Although the CUB2.0 and Unified models do vary laterally, in the study region they vary quite slowly and capture little of the variability of observed travel times. All three models predict Pn travel times that are systematically too fast. These baseline errors range from 2-4 seconds. For this initial round of tomography we stretched the ak135 model to a crustal thickness of 45 km for the reference model.
Download or read book The Structure of the Earth s Crust written by Stephan Mueller and published by Elsevier. This book was released on 2013-10-22 with total page 379 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developments in Geotectonics 8: The Structure of the Earth's Crust Based on Seismic Data covers the papers presented at an International Upper Mantle Committee (lUMC) symposium called ""Crustal Structure Based on Seismic Data"", held on July 30-31, 1971. The book focuses on the structure, composition, and characteristics of the earth's crust. The selection first offers information on the crustal structure of Central and Southeastern Europe by data of explosion seismology; structure of the earth's crust on the territory of the U.S.S.R.; and seismic studies of low-velocity layers and horizontal inhomogeneities within the crust and upper mantle on the territory of the U.S.S.R. The text also takes a look at the deep seismic investigations in the Baikal rift zone and crust of the arctic seas of Eurasia. Discussions focus on peculiarities of crustal structure, structure of the uppermost mantle, and method of investigation. The publication takes a look at the crustal structure of Japan as derived from explosion seismic data; crustal structure in the Matsushiro earthquake swarm area; and Soviet seismic studies of the earth's crust in the Pacific Ocean during the International Upper Mantle Project. The selection is a dependable source of information for readers interested in the structure of the earth's crust.
Download or read book IMPROVED GROUND TRUTH IN SOUTHERN ASIA USING IN COUNTRY DATA ANALYST WAVEFORM REVIEW AND ADVANCED ALGORITHMS written by and published by . This book was released on 2009 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new catalog of seismicity at magnitudes above 2.5 for the period 1923-2008 in the Iran region is assembled from arrival times reported by global, regional, and local seismic networks. Using in-country data we have formed new events, mostly at lower magnitudes that were not previously included in standard global earthquake catalogs. The magnitude completeness of the catalog varies strongly through time, complete to about magnitude 4.2 prior to 1998 and reaching a minimum of about 3.6 during the period 1998-2005. Of the 25,722 events in the catalog, most of the larger events have been carefully reviewed for proper phase association, especially for depth phases and to eliminate outlier readings, and relocated. To better understand the quality of the data set of arrival times reported by Iranian networks that are central to this study, many waveforms for events in Iran have been re-picked by an experienced seismic analyst. Waveforms at regional distances in this region are often complex. For many events this makes arrival time picks difficult to make, especially for smaller magnitude events, resulting in reported times that can be substantially improved by an experienced analyst. Even when the signal/noise ratio is large, re-picking can lead to significant differences. Picks made by our analyst are compared with original picks made by the regional networks. In spite of the obvious outliers, the median ( -0.06 s) and spread (0.51 s) are small, suggesting that reasonable confidence can be placed in the picks reported by regional networks in Iran. This new catalog has been used to assess focal depth distributions throughout Iran. A principal result of this study is that the geographic pattern of depth distributions revealed by the relatively small number of earthquakes (~167) with depths constrained by waveform modeling (+/- 4 km) are now in agreement with the much larger number of depths (~1229) determined using reanalysis of ISC arrival-times (+/-10 km), within their respective errors. This is a significant advance, as outliers and future events with apparently anomalous depths can be readily identified and, if necessary, further investigated. The patterns of reliable focal depth distributions have been interpreted in the context of Middle Eastern active tectonics. Most earthquakes in the Iranian continental lithosphere occur in the upper crust, less than about 25-30 km in depth, with the crustal shortening produced by continental collision apparently accommodated entirely by thickening and distributed deformation rather than by subduction of crust into the mantle. However, intermediate-depth earthquakes associated with subducted slab do occur across the central Caspian Sea and beneath the Makran coast. A multiple-event relocation technique, specialized to use different kinds of near-source data, is used to calibrate the locations of 24 clusters containing 901 events drawn from the seismicity catalog. The absolute locations of these clusters are fixed either by comparing the pattern of relocated earthquakes with mapped fault geometry, by using one or more cluster events that have been accurately located independently by a local seismic network or aftershock deployment, by using InSAR data to determine the rupture zone of shallow earthquakes, or by some combination of these near-source data. This technique removes most of the systematic bias in single-event locations done with regional and teleseismic data, resulting in 624 calibrated events with location uncertainties of 5 km or better at the 90% confidence level (GT590). For 21 clusters (847 events) that are calibrated in both location and origin time we calculate empirical travel times, relative to a standard 1-D travel time model (ak135), and investigate event to station travel-time anomalies as functions of epicentral distance and azimuth. Substantial travel-time anomalies are seen in the Iran region which make accurate locations impossible unless observing stations are at very short distances (less than about 200 km) or travel-time models are improved to account for lateral heterogeneity in the region. Earthquake locations in the Iran region by international agencies, based on regional and teleseismic arrival time data, are systematically biased to the southwest and have a 90% location accuracy of 18-23 km, with the lower value achievable by applying limits on secondary azimuth gap. The data set of calibrated locations reported here provides an important constraint on travel-time models that would begin to account for the lateral heterogeneity in Earth structure in the Iran region, and permit seismic networks, especially the regional ones, to obtain in future more accurate locations of the earthquakes in the region.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1976 with total page 984 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Regional Investigation of Crustal Structure Using Integration of Seismic and Potential Field Data Northern Rockies Great Plains Region written by Bryce Evan Jensen and published by . This book was released on 2010 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Earth Resources written by and published by . This book was released on 1982 with total page 824 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Structure of the Earth s Crust Based on Seismic Data written by Stephan Mueller and published by . This book was released on 1973 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geo Abstracts written by and published by . This book was released on 1978 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Seismological Research Letters written by and published by . This book was released on 1999 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Earth Resources written by and published by . This book was released on 1982 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: A selection of annotated references to unclassified reports and journal articles that were introduced into the NASA scientific and technical information system and announced in Scientific and technical aerospace reports (STAR) and International Aerospace Abstracts (IAA).
Download or read book A History of Persian Earthquakes written by N. N. Ambraseys and published by Cambridge University Press. This book was released on 2005-11-10 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study of the historical seismicity of Iran over the last thirteen centuries.
Download or read book Earth Resources A Continuing Bibliography with Indexes Issue 34 July 1982 written by and published by . This book was released on 1982 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Routine Data Processing in Earthquake Seismology written by Jens Havskov and published by Springer Science & Business Media. This book was released on 2010-06-16 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this book is to get a practical understanding of the most common processing techniques in earthquake seismology. The book deals with manual methods and computer assisted methods. Each topic will be introduced with the basic theory followed by practical examples and exercises. There are manual exercises entirely based on the printed material of the book, as well as computer exercises based on public domain software. Most exercises are computer based. The software used, as well as all test data are available from http://extras.springer.com. This book is intended for everyone processing earthquake data, both in the observatory routine and in connection with research. Using the exercises, the book can also be used as a basis for university courses in earthquake processing. Since the main emphasis is on processing, the theory will only be dealt with to the extent needed to understand the processing steps, however references will be given to where more extensive explanations can be found. Includes: • Exercises • Test data • Public domain software (SEISAN) available from http://extras.springer.com
Download or read book The Geology of Continental Margins written by C.A. Burk and published by Springer. This book was released on 2013-12-20 with total page 976 pages. Available in PDF, EPUB and Kindle. Book excerpt: The continental margins of the world constitute the most impressive and largest physiographic feature of the earth's surface, and one of fundamentally great geological significance. Continental margins have been the subject of increasing attention in recent years, an interest focused by a body of new data that has provided new insights into their character. This interest was further stimulated by the realization that, in addition to the abundant living resources, continental margins contain petroleum and mineral resources that are accessible with existing technology. This realization, along with their basic geological importance, has provoked further research into the nature of continental margins throughout the world. A summary of these findings, as related to both recent and ancient continental margins, is the subject of this book. At various times in the past we had been approached individually to prepare a basic reference to continental margins; we then proposed to do such a volume jointly. However, the stimulus for the present volume eventually arose from a Penrose Conference arranged through the Geological Society of America. This conference was attended by specialists of numerous disciplines and from throughout the world, many of whom insisted that such a volume would be both timely and useful. Consequently, we agreed to undertake the task of assembling this book, with the objectives of making it available as soon and as inexpensively as possible.
Download or read book Iran s Political Demographic and Economic Vulnerabilities written by Keith Crane and published by Rand Corporation. This book was released on 2008 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph is intended to help analysts and policymakers assess the political, demographic, and economic vulnerabilities of Iran to potential U.S. policy measures. The study dissects the political complexities and vulnerabilities of the Iranian government, evaluates ethnic and demographic tensions in Iran, and assesses recent economic developments and potential trajectories of future economic growth. It concludes with a set of policy recommendations for the U.S. government based on the analysis.
Download or read book Petroleum Abstracts written by and published by . This book was released on 1992 with total page 1716 pages. Available in PDF, EPUB and Kindle. Book excerpt:
