Download or read book Wide angle Seismic Profiling of Southern Tibet written by Yizhaq Makovsky and published by . This book was released on 1997 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Processing Modelling and Interpretation of the GEDEPTH Wide angle Seismic Reflection Data from Southern Tibet written by Olumuyiwa Olubusuyi Kola-Ojo and published by . This book was released on 1998 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zs.-Fassung ; Abstract.

Download or read book Processing Analysis and Interpretation of Deep Seismic Reflection Data from the Tibetan Plateau written by Douglas Eric Alsdorf and published by . This book was released on 1996 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Seismic Reflection and Tectonic Studies of the Central Himalayas Southern Tibet written by Michael Lee Hauck and published by . This book was released on 1997 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study of Long Range Seismic Profile Data in Western China written by and published by . This book was released on 2007 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pn Spectra are collected from three PASSCAL seismic experiments in the Tibetan Plateau (TP) over four path groups. The first and second path groups run southward from the eastern Tarim Basin to stations in north and south central Tibet. The third and fourth path groups form two NNE-oriented profiles in the eastern TP. Events recorded by the first 2 path groups also are recorded by the Khyrghistan network (KNET) to the west. A comparison of Pn spectra averaged over both path groups and KNET reveal that mantle lid under the TB attenuates P waves more severely than central Asia, particularly at high frequencies (> 1 Hz). Apparent Q(sub 0) and eta (Pn Q at 1 Hz and its frequency dependence, respectively) are estimated with a simplified geometrical spreading. Over path group 1 that heavily samples northern TB, Q(sub 0) and eta are estimated to be 183 +/- 33 and 0.3 +/- 0.1, respectively. Over path groups 2 and 3 that sample either a mixture of northern and southern Tibet or eastern Tibet, the estimated Q(sub 0) and eta are between approx. 250 and 270 and 0.0 and 0.1, respectively. Over the fourth path group that samples the easternmost TB the respective estimates are 374 +/- 51 and 0.3 +/- 0.1. A comparison of Pn attenuations in continental regions suggest that they are similar in the easternmost TB, Central Asia, Scandinavia, and the Canadian shield. Northern Tibet has the highest attenuation at all frequencies. Pn attenuation under southern Tibet is similar to the shield regions at low frequencies (

Download or read book Wide angle Seismic Recordings Obtained During the Tact Multichannel Reflection Profiling in the Northern Gulf of Alaska written by Thomas M. Brocher and published by . This book was released on 1990 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book INDEPTH Seismic Refraction Analysis of the Yadong Gulu Rift written by Michael J. Cogan and published by . This book was released on 1995 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Deep Seismic Bright Spots written by Andrew Ronald Ross and published by . This book was released on 1999 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crustal Structure and Tectonics of Northeast Tibet from Controlled Source and Broadband Seismology written by Marianne Sherman Karplus and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation I present my contributions to our understanding of three-dimensional crustal structure and plateau growth in the north Tibetan Plateau from the Qiangtang terrane to the Qaidam Basin. Tibet is an ideal location to study plateau development processes in an active continent-continent collision zone. Recent seismic projects have collected an abundance of seismic data in north Tibet, and I use a range of active- and passive-source seismic data to investigate tectonic processes in that area. In particular, I look at how north Tibet is deforming in response to the India-Asia collision including whether there may be mid-or lower-crustal flow within the plateau. I further probe the causes of crustal thickness changes across the plateau and whether the plateau is actively growing. I also ask whether there is present-day subduction of Eurasia beneath north Tibet and what role the Kunlun strike-slip fault plays in the regional tectonics. I derive a velocity model from wide-angle reflection and refraction data using a high-resolution, 270-km active-source seismic profile crossing the Kunlun Mountains and south Qaidam Basin. The central Qaidam Basin resembles average continental crust, whereas the Songpan-Ganzi terrane and East Kunlun Mountains exhibit thickened, lower-velocity crust also characteristic of southern Tibet. Using that method along with P-wave receiver function imaging, I describe details of the crustal thickness change from 70 km beneath the Kunlun Mountains to 50 km beneath central Qaidam. In contrast to previous work, I relocate the change in crustal thickness to ~45 km north of the Kunlun Mountains topographic front, in a region of overlapping bright Moho reflectors at ~70 km and ~50 km. The crustal thickness change is unrelated to the strike-slip North Kunlun Fault. I further discuss differences in Vp/Vs across the terranes and calculate the Vp/Vs of the lower crustal material between the deep and shallow Mohos. Crustal velocities and impedance contrasts suggest that instead weak Tibetan lower crust is injected northward beneath stronger Qaidam crust without southward subduction of Eurasian lithosphere. Finally, at the broadest scale, I use ambient noise tomography to map regional differences in crustal Rayleigh wave group velocities across a larger area of north Tibet including the Qiangtang terrane. For periods of 8-24 s (sampling from ~10-35 km depth within the crust), I observe striking velocity changes at the major east-west Bangong-Nujiang and Jinsha suture zones as well as the Kunlun-Qaidam boundary. I see higher velocities beneath the Lhasa terrane, lower velocities beneath the Qiangtang, then higher velocities in the Songpan-Ganzi, and finally low velocities beneath the Qaidam Basin. Mid-to-upper crustal velocities also change laterally within the Songpan-Ganzi terrane, perhaps indicating subterrane boundaries, as hypothesized previously from geologic data. No velocity change is observed at the active North Kunlun Fault for periods 8-12 s, but for periods 18-24 s (~20-35 km depth) the wedge of Songpan-Ganzi crust between the South and North Kunlun Faults appears lower velocity than the surrounding Songpan-Ganzi terrane and Kunlun Mountains. Velocities west of ~93° E appear higher velocity than the Songpan-Ganzi terrane to the east. Finally, much of north Tibet (~ 32°-36° N) is underlain by a low velocity zone (LVL) at ~20-30 km depth.

Download or read book Investigating the Tibetan Crust Through Automatic S Wave Detection and Travel time Tomography Using the Hi CLIMB Seismic Array written by Evan Riddle and published by . This book was released on 2015 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Hi-CLIMB broadband seismic experiment (2002-2005) operated 233 stations along an 800 km long north-south line from the Himalayan foreland into the central Tibetan Plateau and in a 350x350 km sub-array within southern Tibet and central and eastern Nepal. Station spacing was approximately 8 km along the line and 50 km within the sub-array. The experiment spanned the Himalayan range, Lhasa Block, Qiangtang Block and crossed the Yarlung Tsangpo Suture (YTS) and the Banggong-Nujiang Suture (BNS). From June 2004 to August 2005, over 22,500 local and regional seismic events were recorded throughout the south-central Tibetan Plateau based on automated arrival time picks. This dataset provides an opportunity to jointly invert for crust and upper mantle velocity structure along with earthquake locations using both P and S waves. Automated P and S wave picks, however, were originally determined from vertical component data using short term average to long term average (STA/LTA) windows, resulting in relatively few S picks of generally low quality. To increase the number of accurate S arrivals, we implemented an automatic S-wave picker, which uses signal attributes from three-component seismic data. The signal attributes used are rectilinearity, directivity relative to incoming P wave, ratio of transverse to overall energy and transverse amplitude. An S pick is declared when the combination of signal attributes reaches a noise dependent threshold. We used manual picks and S phase observations from events throughout south-central Tibet to adjust picking parameters and thresholds to optimize automatic S picks. For shallow events we found S[subscript g] can be picked reliably to the S[subscript g]/S[subscript n] crossover distance of approximately 3° while S[subscript n] arrivals are absent. Deep events beneath the southern Tibetan Plateau and the High Himalayas produce clear S arrivals that can be picked to about 7° distance. Applying the S-picker to over 5,700 larger (M[subscript L]≥2.7), well-recorded events led to about 100,000 S picks, significantly increasing the number of arrivals and improving their accuracy. Compared to STA/LTA picks, the new automatic S picks show a decrease in average arrival time residual by over 30 percent. This new polarization picking process allowed us to increase ray coverage, which is crucial for P and S wave structural inversions. With the new automatic arrival time picks we use tomoDD double-difference tomography to invert for crust and uppermost mantle structure beneath the Tibetan Plateau. We use the same subset of over 5,700 best-recorded local events containing over 200,000 P and 100,000 S wave arrivals to conduct the inversion. In the upper crust we observe extensive low velocity zones extending to 25 km depth. Based on Vp and Vp/Vs results we suggest this material is quartzite and highly felsic granite. Beneath the BNS we image low Vp values and increased seismicity, indicating a possible fault zone down to 25 km depth. In the lower crust beneath the Qiangtang Block we image high Vp and increased seismicity, suggesting an area of increased crustal strength to the north. Beneath the High Himalaya, south of YTS, the Moho depth decreases from 55 to 75 km depth as the Indian plate subducts beneath Tibetan crust. Along the Moho we observe Vp values upwards of 8.5 km/s extending to 31°N. We attribute these high velocities to the formation of eclogite along the base of the Indian plate, which terminates at 31°N as upper mantle velocities drop to 8.2 km/s. In the lower crust beneath the Lhasa Block low Vp values, around 6.5 km/s, extend to near Moho depth. A lack of seismicity is also present, which could indicate a weak and possibly ductile lower crust in the Lhasa Block. Nowhere in the lower crust does the Vp/Vs ratio exceed 1.8 suggesting extensive areas of partial melt are unlikely.

Download or read book Crustal Structure of Northeast Tibet from Wide angle Reflection and Refraction Velocity Modelling written by Kieran Kraus and published by . This book was released on 2015 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Deep Seismic Profiling of the Continents written by and published by . This book was released on 1996 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Tomographic Analysis of the Wabash Valley Seismic Zone written by Bill Sweidan and published by . This book was released on 2021 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Wabash Valley Seismic Zone (WVSZ), or Wabash Valley Fault System (WVFS), is an intraplate region of higher-than-average seismicity located within the Illinois Basin. This region has produced three 5.0+ magnitude earthquakes within the last 50 years, and recent paleoseismological studies have also shown evidence for 7.0+ magnitude events occurring within the history of the fault system. The prominent faults within the system have very little surface expression, so available data of the orientation, trend, and extent of the fault system comes from seismic reflection data and are observed at depth within mine shafts throughout Illinois. The Wabash Valley faults are contained between the LaSalle Anticlinal Belt, a prominent Precambrian complex of en echelon folds to the north, and the junction of the east/west trending Cottage Grove and Rough Creek faults to the south. Most of the faults trend to the NE and can display vertical offsets into the hundreds of meters, penetrating the Precambrian basement rock at depth. Though there are some similarities in fault orientation and trend to the faults contained within the New Madrid Seismic Zone to the SE, the possible connection to and the tectonic setting of the Wabash Valley Seismic Zone is ambiguous. As part of the Earthscope project to map the crustal structure of the North American continent, data was passively collected along a 400-kilometer Flexible Array across Illinois and Indiana for the purpose of wide angle and deep seismic profiling in the form of tomography. Utilizing a new ray tracing methodology based on Dijkstra's algorithm, tomograms of the study area were created by inverting for Vp data collected from this array. Our tomograms show no evidence for a rift pillow system under the Wabash Valley as predicted, but there is evidence for a dipping fast anomalous zone that has been previously hypothesized from reprocessed COCORP data. We consider this COCORP reflector as an upper layer of eclogite above old, subducted crust with a higher impedance contrast than the surrounding mantle material. Further investigation is warranted, particularly with respect to ray directionality as rays arriving from north of the array do not travel through the fault system itself, whereas southern rays do. It is our hope that further studying including only southern ray paths may illuminate a supposed rift pillow system.

Download or read book Growth and Collapse of the Tibetan Plateau written by Richard Gloaguen and published by Geological Society of London. This book was released on 2011 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: Despite agreement on first-order features and mechanisms, critical aspects of the origin and evolution of the Tibetan Plateau, such as the exact timing and nature of collision, the initiation of plateau uplift, and the evolution of its height and width, are disputed, untested or unknown. This book gathers papers dealing with the growth and collapse of the Tibetan Plateau. The timing, the underlying mechanisms, their interactions and the induced surface shaping, contributing to the Tibetan Plateau evolution are tightly linked via coupled and feedback processes. We present interdisciplinary contributions allowing insight into the complex interactions between lithospheric dynamics, topography building, erosion, hydrological processes and atmospheric coupling. The book is structured in four parts: early processes in the plateau formation; recent growth of the Tibetan Plateau; mechanisms of plateau growth; and plateau uplift, surface processes and the monsoon.

Download or read book Exploring the Earth s Crust written by C. Prodehl and published by Geological Society of America. This book was released on 2012 with total page 784 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This volume contains a comprehensive, worldwide history of seismological studies of the Earth's crust using controlled sources from 1850 to 2005. Essentially all major seismic projects on land and the most important oceanic projects are covered. The time period 1850 to 1939 is presented as a general synthesis, and from 1940 onward the history and results are presented in separate chapters for each decade, with the material organized by geographical region. Each chapter highlights the major advances achieved during that decade in terms of data acquisition, processing technology, and interpretation methods. For all major seismic projects, the authors provide specific details on field observations, interpreted crustal cross sections, and key references. They conclude with global and continental-scale maps of all field measurements and interpreted Moho contours. An accompanying DVD contains important out-of-print publications and an extensive collection of controlled-source data, location maps, and crustal cross sections."--Publisher's description.

Download or read book The Solid Earth written by C. M. R. Fowler and published by Cambridge University Press. This book was released on 2005 with total page 746 pages. Available in PDF, EPUB and Kindle. Book excerpt: A fully up-dated edition of this acclaimed undergraduate geophysics textbook.

Download or read book Seismology and Structure of the Earth written by Barbara Romanowicz and published by Elsevier. This book was released on 2010-04-20 with total page 873 pages. Available in PDF, EPUB and Kindle. Book excerpt: Treatise on Geophysics: Seismology and Structure of the Earth, Volume 1, provides a comprehensive review of the state of knowledge on the Earths structure and earthquakes. It addresses various aspects of structural seismology and its applications to other fields of Earth sciences. The book is organized into four parts. The first part principally covers theoretical developments and seismic data analysis techniques from the end of the nineteenth century until the present, with the main emphasis on the development of instrumentation and its deployment. The second part reviews the status of knowledge on the structure of the Earths shallow layers, starting with a global review of the Earth's crustal structure. The third part focuses on the Earth's deep structure, divided into its main units: the upper mantle, the transition zone and upper-mantle discontinuities, the D region at the base of the mantle, and the Earth's core. The fourth part comprises two chapters which discuss constraints on Earth structure from fields other than seismology: mineral physics and geodynamics. Self-contained volume starts with an overview of the subject then explores each topic with in depth detail Extensive reference lists and cross references with other volumes to facilitate further research Full-color figures and tables support the text and aid in understanding Content suited for both the expert and non-expert