Lithospheric Magnetic Anomalies of the Eastern Part of the Arctic Ocean as Images of Tectonic Structures

Izvestiya, Atmospheric and Oceanic Physics - Geomagnetic data measured by the CHAMP satellite have been used to construct the spatial distribution of the lithospheric magnetic anomaly field in the...     

Microseismicity in Local Areas: The Southeastern Part of the Fennoscandian Shield

This paper summarizes the observations of microseismic emissions by these authors in several areas of the Russian part of the Fennoscandian Shield to assess the potential of microseismicity to determine the present-day activity of local features in the upper part of the geologic medium. We give amplitude–frequency characteristics and the space–time distribution of naturally occurring microseismic events that are hypothesized to be of endogenous origin. We discuss the relationships these characteristics have to the regional geodynamic setting, average dimensions, and petrographic composition of active rock blocks.     

Granitoids of the Kongo Magmatic Zone of the Omolon Massif (Northeastern Russia): Rock Composition,Age, and Geodynamic Setting

Geotectonics - In our study we analyzed the composition of granitoid rocks within the Kongo magmatic zone of the Omolon median mass. The studied calc-alkaline granitoids cut through the Early...     

PHASE DISTORTION DUE TO ABSORPTION IN SEISMOGRAMS AND VSP*

Absorption of seismic energy in the earth reduces amplitudes and changes phases of the propagating seismic waves. Amplitudes are usually recovered according to an estimated exponential decay curve, while phase distortions are generally disregarded. Therefore, accurate processing of seismic data requires a careful investigation of the relationship between absorption and phases. In this paper a procedure is suggested to achieve this goal, and some related topics are worked out. A method is outlined for computing synthetic seismograms and vertical seismic profiles with phase distortion due to absorption. The algorithm works in the frequency domain, and it provides for absorption according to the usual model of exponential decay of amplitude with distance. The absorption coefficient is a linear function of frequency and is related to the quality factor Q of the rocks. Complex seismic velocities are introduced and minimum-phase delay due to absorption is assumed for all cases considered. Methods for estimating Q profiles from seismic well surveys and seismic data are described. Comparison between field and synthetic data shows the effectiveness and benefits of the procedure. Some applications of the method to phase distortion recovery and wavelet processing are presented.     

New average global P and PcP travel times

This paper deals with the construction procedure for regional travel-time curves and the new average global curve for P times. This paper also presents new average global values for PcP times constructed from observed travel times.