توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱THE CRUSTAL VALUE OF ATTENUATION IN THE NORTHEAST OF IRAN
اطلاعات انتشار: پنجمین کنفرانس بین المللی زلزله شناسی و مهندسی زلزله، سال
تعداد صفحات: ۹
When a propagating wave is introduced into the Earth from a source, it is recorded with some changes after its travel through the Earth. The most evident of these changes is a loss or attenuation in energy and amplitude. In other words, the Earth introduces a reduction in the amplitude level and a change in the nature of the wavelet, which becomes broader and more asymmetric with increasing length of travel. The study of attenuation in high frequency seismic waves is useful for both the seismologist and the earthquake engineer as it is an essential parameter in predicting the earthquake ground motion in seismic hazard analysis. Why seismic waves attenuate or decrease in amplitude as they propagate? It is known that the reflection and transmission of seismic waves at discrete interfaces reduce their amplitude. There are four other processes that can reduce wave amplitude: geometric spreading, scattering, multipathing, and anelasticity. All four processes are important for seismic waves. The first three are described by elastic wave theory, and can increase or decrease an arrival's amplitude by shifting energy within the wave field. By contrast, anelasticity reduce wave amplitudes only because energy is lost from the elastic waves. The most commonly used measure of attenuation is the quality factor (Q) and its inverse (Q–1. In this study, for the measurement of ?? and Q?? –1, the extended coda normalization method is used (Yoshimoto et al., 1993). Coda normalization method is widely used for the estimation of attenuation per travel distance, site amplification factors, and source spectra on the basis of the spatially uniform distribution of coda energy at a long lapse time. The appearance of coda waves in seismograms is one of the most prominent observations supporting the existence of small–scale random heterogeneities in the earth (Aki, 1980).<\div>

۲CRUSTAL VELOCITY STRUCTURE IN NORTH–EAST OF IRAN, USING ITERATIVE TIME–DOMAIN DECONVOLUTION RECEIVER FUNCTIONS
اطلاعات انتشار: پنجمین کنفرانس بین المللی زلزله شناسی و مهندسی زلزله، سال
تعداد صفحات: ۹
The tectonics of North–east of Iran is a key to understanding the closure processes of the Paleo–tethys oceanics realm as well as associated continental deformation and the crustal study is very important in understanding the tectonic evolution of an area. There is no a number of studies on crustal structure in this area then less is known and little has been published on this problem. This paper presents the results of seismic experiment aimed at the crustal structure beneath the 20 broadband and middle–band seismic stations in Northeast of Iran, using the teleseismic waveform receiver functions technique. An iterative time–domain deconvolution approach is applied to estimate receiver functions. Depth of the Moho and three main parts for crustal structure in northeast of Iran is suggested as: The upper part of crust has an S–wave velocity between 2.4–3.4 km\s and a 11 km thickness as an average with a 2.0 km standard deviation, the middle part of crust has an S–wave velocity between 3.1–3.6 km\s and a 21 km thickness with a 3.3 km standard deviation, the lower crust has an S–wave velocity between 3.6– 4.3 km\s and a 16 km thickness with a 3.3 km standard deviation. The Moho depth is 49 km with 2.0 km standard deviation.<\div>

۳Crustal Velocity Structure in Iranian Kopeh–Dagh, from Analysis of P–Waveform Receiver Functions (انگلیسی)
اطلاعات انتشار: مجله زلزله شناسي و مهندسي زلزله، هشتم،شماره۴، Winter ۲۰۰۷، سال
تعداد صفحات: ۸
In this study, the crustal velocity structure and depth of Moho is determined under the eastern part of Iranian Kopeh Dagh, North–East Iran that is named Hezar–Masjed mountains. The teleseismic waveform receiver functions technique is used to determine crustal thicknesses in this study. 41 teleseismic earthquakes from three broadband seismometers installed in the Iranian Kopeh–Dagh, are used to calculate P–wave receiver functions. Receiver functions for each station are generated from events for a wide range of backazimuths. From analysis of receiver functions at KAR, ZOW and HAM stations, the crustal structure is suggested for the Hezar–Masjed area with a Moho depth of 44–50km. Results indicate three main layers; the upper crust has an S–wave velocity between 2.1–3.2km\s and a 10 to 12km thickness, a middle crust with S–wave velocity between 3.2–3.7km\s and a 22 to 25km thickness and the lower crust with S–wave velocity between 3.7–4.4km\s and a 12 to 15km thickness. An S wave velocity between 4.6–4.7km\s indicates the velocity of the Moho at 47km on average and varies from 44 to 50km. Deeper Moho is found under the southern station
نمایش نتایج ۱ تا ۳ از میان ۳ نتیجه

ارتباط با ما

لینک‌های مفید