Abstract
Large earthquakes occurred in the central part of Kumamoto Prefecture on April 14–16, 2016, causing severe damage to the northern segment of the Hinagu faults and the eastern segment of the Futagawa faults. Earthquake surface ruptures appeared along these faults and on the Aso volcanic edifice, which in turn generated landslides. We conducted landform change analysis of the central cones of Aso volcano by using satellite and aerial photographs. First, we categorized the topographical changes as surface scarps, arc-shaped cracks, and linear cracks. Field survey indicated that landslides caused the scarps and arc-shaped cracks, whereas faulting caused the linear cracks. We discovered a surface rupture concentration zone (RCZ) formed three ruptures bands with many surface ruptures and landslides extending from the west foot to the center of the Aso volcanic edifice. The magmatic volcanic vents that formed during the past 10,000 years are located along the north margin of the RCZ. Moreover, the distribution and dip of the core of rupture concentration zone correspond with the Nakadake craters. We conclude that a strong relationship exists between the volcanic vents and fault structures in the central cones of Aso volcano.Graphical abstract.
Highlights
Previous researches discussed the relationships among major active faults and the locations of volcanic vents created by the faulting. Nakamura (1969) indicated the existence of a strong relationship between regional stress fields and vent distributions observed on Fuji volcano, Izu-Oshima volcano, and Hakone volcano. Watanabe et al (1979) suggested that two old cinder cones known as Akai and Omine that erupted large amount of lava flows at the western side of Aso caldera were located in two small extensional pull-apart structures, where two discontinuous right-lateral strike-slip faults had formed an echelon
The geomorphological variations caused by the Kumamoto earthquakes created an rupture concentration zone (RCZ) with a core composed of Aso-N, Aso-C, and Aso-S rupture bands
It was inferred that the Aso-S rupture band extended to the north Hinoyama tunnel and that Aso-N and Aso-C rupture bands extended to the north Kusasenrigahama area
Summary
Previous researches discussed the relationships among major active faults and the locations of volcanic vents created by the faulting. Nakamura (1969) indicated the existence of a strong relationship between regional stress fields and vent distributions observed on Fuji volcano, Izu-Oshima volcano, and Hakone volcano. Watanabe et al (1979) suggested that two old cinder cones known as Akai and Omine that erupted large amount of lava flows at the western side of Aso caldera were located in two small extensional pull-apart structures, where two discontinuous right-lateral strike-slip faults had formed an echelon. The landslides on the central cones of Aso volcano occurred mainly as earth slides, spread, and flow types based on the surface deposits composed of weathered fine volcanic materials and humic black soil (Fig. 3). The earth slide on the central cones of Aso volcano had a typical rotational shape with concave curve surfaces, flat heads, and transverse cracks or ridges (Fig. 3a). We observed soil ripples around the top of the cone, which indicated that creep-like deformation occurred on the slopes when the cone moved during the earthquakes On the aerial photographs survey, we excluded cracks and scarps caused by landslides, which included earth slides, flows, and creep-like deformation. Many linear cracks with E–W to ESE–WNW orientation appeared between the southern edge of the Nagano
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