Muography. Группа авторов
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Название: Muography

Автор: Группа авторов

Издательство: John Wiley & Sons Limited

Жанр: Физика

Серия:

isbn: 9781119723066

isbn:

СКАЧАТЬ are widely used outdoors (Fig. 3.1). The principle of the spring‐type gravimeters is easily understood by imagining a test mass attached to the end of a spring; a tiny gravity change, Δg, is amplified and observed as a displacement of a spring, Δx, via well‐known Hooke’s law, mΔg=kΔx, where k stands for a spring constant. The stability of the spring constant is precisely controlled by thermostats. Highly stable gravimeters are available, such as Scintrex CG series, Lacoste & Romberg gravimeters, etc. (Seigel et al., 1993). The users of spring‐type gravimeters begin the measurement at reference stations, where the absolute gravity acceleration is known beforehand, and determine the gravity acceleration of outdoor stations by cumulating the gravity differences.

      The main focus of this chapter is to extract the gravitational effect of mass in the near‐surface. It can be done by removing the global trend of the gravity field of the Earth, referred to as the normal gravity field. The normal gravity field is defined by the equatorial radius of the Earth, the geocentric gravitational constant of the Earth, the dynamical form factor of the Earth, and the angular velocity of Earth rotation (Torge & Müller, 2012). According to Torge & Müller, 2012, the normal gravity is expressed as a function of geographic latitude ϕ

Schematic illustration of geometrical relationship between the gravitational, centrifugal, and gravity acceleration on the Earth.

      which is accurate to 1 μms−2. The change of the normal gravity with height is given as

Schematic illustration of the free-air gravity anomaly can be decomposed into the three terms: the gravitational contribution of the target volume, that of the topographic mass and the regional trend.

      The first term, Δg target, is the gravitational effect of the masses within the target volume of the survey, whose density distribution we wish to solve by inversion analysis. The second term, Δg terrain, is the effect of topographic mass outside СКАЧАТЬ