Geophysical Survey

About: Geophysical Survey is a facility organization based out in Obninsk, Russia. It is known for research contribution in the topics: Geology & Seismology. The organization has 308 authors who have published 256 publications receiving 3067 citations. The organization is also known as: Federal State Institution of Science Geophysical Survey of the Siberian Branch of the Russian Academy of Sciences.

A geophysical study of Nelson — Cook Strait region, New Zealand

Abstract: Recent magnetic and gravity surveys in the Nelson region permit a fuller discussion of the nature of the long major magnetic anomaly associated with the trend of the Nelson Syncline. The previous view that the anomaly is due to buried Upper Paleozoic igneous rocks such as the Brook Street Volcanics and Rotoroa Igneous Complex is held to be incompatible in some ways with the relationships between gravity and magnetic force values and with the physical properties of these rocks. It is suggested that a buried serpentinised ultramafic system might be the most appropriate geological model to explain the anomalies; and that the Dun Mountain Ultramafics may either have been emplaced directly from this system, or may be the surface expression of these anomalies displaced to the east as part of a sheet-type movement.

Detection of radar signals with large radar signatures

Abstract: Method and apparatus for generating and receiving carrier-free radar pulses that can be detected even though they are heavily distorted by a target and have additive noise superimposed on them, or are in an environment of unwanted signals. The method is especially applicable to signals that are based on pulses with a duration of 1 nanosecond (ns) or less. The radar signature of typical targets from such signals is very large, which makes it hard to selectively receive return signals unless they are marked. Fine structure marking is not effective for such short duration pulses. A method for organizing the signal with coarse structure marking is described that allows the radar receiver to discriminate heavily distorted wanted signals from unwanted signals and noise without requiring large peak power at the transmitter. The disclosed method involves placing positive-going and negative-going pulses together in a pattern of contiguous pulses to form a character. Generating one or more time-delayed replicas of the character and summed selected ones together to form a signal with coarse structure marking. The delay time of each replica may vary and some replicas may have their polarity reversed before summing, but all are based on pulses that are short enough to imply that most return pulses would not be recognized by a receiver. However, the coarse structure of this invention marks the signal for selective reception. It renders the characters within it recognizable, and thereby enables the transmission of pulses without a fine structure marking which might otherwise be absorbed by the atmosphere.

Radiator for slowly varying electromagnetic waves

Abstract: A radiator useful for radiating pulses with a duration of about 10 ms is disclosed. Such pulses occupy the frequency band from zero to a few hundred Hertz. For a given time variation of an electromagnetic signal, the energy radiated in the far field is proportional to (Is) 2 , where I is the current amplitude in the antenna and s is the length of the radiator. Typical antenna designs cannot be used at very low frequencies with large relative bandwidths. However, the large current radiator disclosed, herein, is small, has antenna currents in the order of 10 8 A, and requires a drive voltage of about 1 volt and drive current of 10 4 A. This large current radiator is designed with a small antenna length s by using a design wherein the antenna current is n times larger than the drive current. This is accomplished by winding electrically conductive means n times around a shield so that the n forward loop wires are all on one side of the shield, and cover a surface area sxW. The n return loop wires are on the opposite side of the shield and are confined so that they cover a surface area that is very small compared to the area of the forward loop. Furthermore, the shield is fabricated to reflect the electromagnetic energy produced by the forward loop and absorb the electromagnetic energy produced by the return loop. Hence, the antenna is highly efficient. And, since n can be 10,000 or more, the antenna current can be in the kilo Ampere range and beyond with a moderate drive current.

Do seismologists agree upon epicentre determination from macroseismic data? A survey of ESC Working Group ' Macroseismology'

Abstract: In contrast to the case of instrumental data, the procedures for epicentral parameter determination (coordinates and I0) from macroseismic data are not very well established Although there are some "rules", upon which most seismologists agree (centre of the isoseismal of largest degree, and so on), the practical application of, such rules displays many problems Therefore, it is commonly seismologists' practice to find their own pro cedures and solutions; this is particularly evident in the more complicated cases, Such as offshore epicentres or, as in many cases of historical earthquakes, poor sets of data One of the major consequences is that parametric catalogues are not homogeneous with respect to macroseismic parameters; moreover, merging catalogues compiled according to different criteria can introduce high noise in any catalogue built in such a way In order to survey the current practice of epicentre determination from macroseismic data in Europe, a set of cases was distributed to the participants of the first meeting of the ESC WG "Macroseismology" A comparison of the 15 sets of results provided by 16 authors, who gave their own solutions and the explanation, of the adopted procedures is given, showing that in some cases the ideas and results are rather distant