Fig. 1. Horizontal displacement of the second and third order triangulation points accompanied with the Tottori Earthquake of (after SATO, 1973)

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1 Journal of the Geodetic Society of Japan Vol. 27, No. 3, (1981), pp Research on Fault Movement by means of Aero-Triangulation ( T) (An experiment on the earthquake fault of the Izu-Oshima Kinkai Earthquake of 1978) Hiroshi SATO Faculty of Sciences, Hirosaki University and Seizo KAKISHITA Kokusai Aero-Survey Company (Received October 20, 1981) ABSTRACT An experiment of aero-triangulation has been made in Izu Peninsula for the purpose of detecting the fault movement of the Izu-Ohshima Kinkai Earthquake by means of aero-survey, instead of ground triangulation. The measurement in Inatori area where a trace of earthquake fault was found gives a nearly same result as the one obtained from field investigations, that is, relative displacement of the Inatori-Omineyama Fault was measured as about one meter in average. The experiment in Hachiyama area shows a clear discontinuity of about 80 cm in the horizontal displacement vectors along the fault line estimated from seismological and geodetic data, though any remarkable fault trace was not found there. The results of present experiment suggest that the method of aero-triangulation is usef ull means for the detection of earthquake fault.

2 Fig. 1. Horizontal displacement of the second and third order triangulation points accompanied with the Tottori Earthquake of (after SATO, 1973) Fault length : 33 km, Fault width : 13 km, Average dislocation : 2.5 m, Rupture velocity : 2.3 km/sec, Rise time: 3 sec, Particle velocity: 42 cm/sec, Stress drop: 83 bar, Effective

3 Table 1. List of Revision Surveys Fig. 2. Distribution of after shocks and the fault model of the Izu-Oshima Kinkai Earthquake of (after SHIMAZAKI and P. SOMMERVILL, 1978).

4 Fig. 3. Fault trace of the Izu-Oshima Kinkai Earthquake (after MURAL et al. 1978).

5 Fig. 4. Maximum acceleration in the Izu Peninsula estimated from damages due to the earthquake of 1978, and the numbers of small land slides. (Compiled from the report of Nihon Doro Kyokai, 1978)

6 Fig. 5. Principle of aero-triangulation.

7 Fig. 6. Horizontal displacement vectors near Inatori measured with the method of aero-triangulation. The dash line show the fault trace. Fig. 7. Circle diagram of vectors.

8 Fig. 8. Horizontal displacement vectors by aero-triangulation near Hachiyama.

9 [1] KASAHARA, K.: The nature of seismic origins as inferred from seismological and geodetic observation (1), Bull. Earthque. Res. Inst., 35, (1957), [2] CHINNERY, M. A.: The deformation of the ground around surface faults, Bull. Seism. Soc. Am., 51, (1961), [3] KANAMORI, H.: Determination of effective tectonic stress associated with earthquake faulting, the Tottori Earthquake of 1943, Phys. Earth. Planet. Interiors, 5, (1972), [4] SATO, H.: A study of horizontal movement of the Earth Crust associated with destructive earthquakes in Japan, Bull. Geogr. Surve. Inst. 19, (1973), [5] SHIMAZAKI, K. and P. SOMMERVILL: Summary of the static and dynamic parameters of the Izu-Oshima- Kinkai Earthque. Bull. Earthque. Res. Inst., 53, (1978), [8] INOUCHI, N. and H. SATO: Crustal deformation related to the Izu-Oshima-Kinkai Earthquake of 1978, Bull. Geogr. Surve. Inst., 23, No. 2 (1979),

On the Detectability of Earthquakes and Crustal Movements in and around the Tohoku District (Northeastern Honshu) (I) Microearthquakes Hiroshi Ismi an

On the Detectability of Earthquakes and Crustal Movements in and around the Tohoku District (Northeastern Honshu) (I) Microearthquakes Hiroshi Ismi and Akio TAKAGI Observation Center for Earthquake Prediction,