SIZES AND SOME FEATURES OF LUMINOUS SOURCES ASSOCIATED WITH THE 1995 HYOGO-KEN NANBU EARTHQUAKE

Sources of luminescence and their buildup processes accompanying the 1 995 Hyogo-ken Nanbu earthquake of M 7.2 are studied based on pieces of information obtained mainly by interviewing eyewitnesses. Gross forms of relatively large-scale luminous sources are roughly classified int o four types: lightning with zigzag lines, a swelling shield-shaped so urce, an upward-extending fan-shaped source, and a belt of lights. The last one includes an are-like source. Each source is predominantly in tones of either colorless-white, blue or orange-color. This paper pre sents 23 spottings, distributed as wide as 50 km from the epicenter of the mainshock near Kobe City. Along with these spottings, some local flashing events were reported. The upper limit of the height of severa l sources was able to be estimated as less than 200 m above the ground . The linear dimension of the horizontal extent ranged from about 1 to 8 km. The luminance was estimated to be more than an order of 10(3) c d/m(2) for an are-like orange colored source at the eastern part of th e aftershock area. Not a few sources were glittering more intensely th an this case. According to most of the eyewitnesses, the luminosity st arted from ground level on land, suggesting that discharge processes o f the polarized electricity in near-surface rocks map be the primary d riving force of the luminescence. However, electricity charged in the air should be also responsible to some luminous phenomena, especially a kind of lightning above the sea. Fog or dust was observed in the air in the region around Nishinomiya City, east of Kobe, preceding the qu ake, which might have played the role of an effective electrical condu ctor in glow discharge.