2.3 Advantages of monitoring by meteorology satellite
The surveying coverage of meteorology satellite is very wide, 2800km for a single orbit, an
effective distance is about 1000km. A receiving station can cover 4500km wide and 14 million
square kilometers in area, which is very useful to analyze the crust movement and the magma
activity behavior for a large area, and enhances the accuracy of preceding volcanic eruption.
3. Feature of abrupt geothermal anomaly in volcanic region
According to the now generally accepted “plate-tectonics” theory, scientists believe that the
Earth’s surface is broken into a number of shifting slabs or plates, which average about 50 miles in
thickness. These plates move relative to one another above a hotter, deeper, more mobile zone at
average rates as great as a few inches per year. Most of the world’s active volcanoes are located
alone or near the boundaries between shifting plates and are called “plate-boundary” volcanoes.
Also, volcano emanation is a form of strong release of substance and energy inside the Earth.
When cold oceanic plates go down to one side of island arc from oceanic trench, during the initial
period, volcanic activity could not be caused in virtue of low temperature. Crush materials melt
under the action of various stresses at a specified distance and depth of the plates (You et al.,
1998). Thus, melting substances will erupt from rock faults or rupture belts under the action of
high pressure (Song et al., 1990; Jin et al., 1994). During the development of volcano, abrupt
geothermal anomaly definitely occurs at repeated times, however, pocket of magma detained at
shadow crush is only the ideal spot hot source of geothermal anomaly in volcanic region. Deep
melting magma in the course of moving up by high pressure excites pocket of magma. Therefore,
the existed anomalous subterranean heat is aroused into abrupt geothermal anomaly. Different
types of volcanoes have different geothermal features. Studying different types of geothermal
features and intensity of volcano activity is one of thermal infrared remote sensing monitoring and
forecasting.
The newer age and the bigger scale of volcanic activity is, the more possible the formation of
high temperature anomaly. From the view of global, dejected or expanding acid volcanoes are
interrelated with the high temperature water-heat system, but not slab basic volcanoes do. This is
because rocks erupted by basic volcanoes have vanished by the remaining heat of rock bodies.
Pocket of magma necessary to form the high temperature water-heat system is not held up in the
crushed shadow of volcanic region, so that there is not a direct heat source to increase ground
temperature. The volcanic region at Changbai Mountain fully reflects this feature. The volcano of
Changbai Mountain erupted mainly on crack; since 2 Ma, it has changed into central acid eruption,
and pocket of magma would be found at 15km depth of heavenly pool. The characteristics might
become an ideal condition providing to forecast the abrupt geothermal anomaly prior to volcano
eruption.
4. Analysis of transmission mechanism of geothermal anomaly in volcanic
region
The deep terrestrial heat in volcanic region might be transmitted to surface through various
transmission mechanisms. During the dormant period of volcano, volcanic areas have a
phenomenon of geothermal anomaly; while in mobile or forewarning period, geothermal anomaly
would be more obvious than ever. In the course of transmitting to the surface, the deep terrestrial
heat mainly transmits through electromagnetic radiation, conduction of terrestrial heat, convection
of terrestrial heat etc. towards the surface, which makes the terrene’s temperature rise. Besides,
solar radiation also has a certain role on the surface temperature rising.
4.1 Solar Radiation
In days the surface of earth radiated by the Sun makes its temperature rise. In the forewarning
period of volcano activity, substance structure and state will be changed because of geothermal
anomaly. The temperature in anomalous region is higher than in normal region by solar radiation.
This is because a great deal of high temperature’s magma goes up to crush and heats country rocks.
Vapors in country rocks and soils greatly evaporate. When they meet chilled junction in the
surface, it will make the content of water in substance increase, which can change the structure of
water layers of soils and rocks, and get heat capacity of substance larger. This shows that
substances are very capable of storing heat. There is an obvious difference for the temperature
indicator between anomalous and normal areas.
