Although earthquakes are the destructive phenomenon of the crust, the observation is to the foundations of the earthquake prediction and volcanic eruption prediction research. Always, as observation equipment, this observatory holds 16 networks of seismic observation of the central part and the northern part areas in Kyushu, and 9 networks of seismic observation of the Unzen volcano area, and is performing continuation observation on the real time by telemeter.
As for this telemetry system for observation of earthquakes, four points were first equipped as the part of the first and secondary volcanic eruption prediction plan (1974-1983), and they are the purpose which grasp movement of magma to the highest peak of Mt.Fugen which is the eruption point since the history started, from the Chijiwa caldera of the Unzen volcano western side assumed at the time of the eruption, and they are arranged so that these may be surrounded. After that, it inherits in the 5th earthquake prediction plan (1984-1988), and was expanded on the total observation network of 11 points for the Amakusa graben and the Shimabara-Kumamoto graben, which are earthquakes frequent occurrence zones. Furthermore, in the 6th and the 7th earthquake prediction plan (1988-1998), the extension to the observation network for the whole region of the central part and the northern part of Kyushu is achieved, and it is always observing by 16 observing points of earthquakes now.
The data signal from the observing point of
every place is conveyed by the cable telemetry system by NTT dedicated
line (D1 standard) in the Shimabara base observatory, and is acting
as the monitor by Pen Recorder for a long time. Furthermore, earthquake
data automatic processing equipment introduces, it comes to perform
automatic focus determination processing of earthquakes, and the
grasp of a quick earthquake generating situation came to be made
One of the axes presumed to have arranged like the group of a wild goose in the Beppu-Shimabara graben is the Unzen graben that is crossing the central part of the Shimabara peninsula. Now, sedimentation is continued at the rate of 2 to 3mm per year. Moreover, the western Chijiwa bay is also presumed to be that which sediments doubly and forms the fan in the meeting point with the Amakusa graben, which stands in the row in south-southwest.
In order to grasp the actual condition of these crustal movements, the level point and the reference point for a electro optical distance measurement are installed, cooperation of another universities observation organization is obtained, and the 1st survey was performed in the Shimabara peninsula in 1986. Miraculously, since Mt.Unzen started eruption activity for the first time in 198 years in 1990, the survey is carried out again after that and many results in connection with volcanic eruption prediction research are obtained.
On the one hand, maintenance of crustal-movement observation institution was always accompanied by eruption activity of Mt.Unzen also achieved, and four borehole type tiltmeters were installed on the outskirts of the volcano in 1992. Moreover, crustal-movement observation of Kyushu is also started by introduction of GPS observation equipment.
[Hot spring observations]
The gas ingredient currently emitted from magma melts into underground water, and a hot spring is generated by the interaction with the rock in the wall of a passage. Therefore, hot springs are expected as an important point of the direct communication of information about the activity situation in the volcanic underground depths. An unusual change had actually arisen in states that a hot spring springs out, just before the once large eruption in the Sakurajima volcano. Since it is such, continuous observation of the temperature of a hot spring, water pressure (water level), or a chemistry ingredient is very important in grasping a volcanic activity situation.
In this observatory,the continuous observation
of the quality of hot springs is carried out about the Unzen,
Aso, and Sakurajima, many volcanoes 6 fountainhead. According
to the old result, the concentration in which carbonic acid gas
melts and remains is increasing gradually before an eruption time
and summit activity activated. Moreover, if a summit crater will
be in an opening state, changing to gradual decrease immediately
is also clear. This is reflecting increase and decrease of the
fluid pressure of the gas inside a volcano, and is effective in
evaluation of the degree of volcanic activity, or prediction of
transition. Moreover, in the hot spring observation well currently
installed within the enclosure of this observatory, just before
or after earthquake generating in the neighborhood, an unusual
rise or unusual descent of the water level is see, and reflecting
accumulation and opening of crustal strain sharply is verified.
[Volcanic gas observations]
The volcanic gas (smoke) currently emitted from the crater precedes and increases to an eruption, and it is expected that change is seen by the chemistry composition.
In this observatory, telemetry of the amount to which the sulfur dioxide(SO2) is emitted from the summit crater is continuously carried out in Asama, Oshima, Aso, and Sakurajima-many volcanoes as a part of the "development research of the new method of the observation of volcanic activity "based on the first and secondary volcanic eruption prediction plan. Moreover, in Mt.Aso, automatic continuation observation of hydrogen fluoride(SO2), HF, hydrogen chloride, and the four ingredients of H2S in the volcanic gas diffused in the atmosphere near the crater was carried out, and it investigated how change of the ratio of the ingredient would be connected with the volcanic activity. In both the volcanoes in Asama and Aso, it precedes with the eruption and the amount to which SO2 are emitted increases. Moreover, in the Aso volcano, it is recognized that the relative concentration of HF or HC1 also increases, as the volcano becomes active.
In recent years, amount of the sulfur dioxide emitted from the Unzen volcano-Kueyama, which became active, was mainly measured repeatedly.