Aspect ratios and magma overpressures of non-feeder dikes observed in the Miyake-jima volcano (Japan), and fracture toughness of its upper part

作者：Kusumoto Shigekazu^*; Geshi Nobuo; Gudmundsson Agust

来源：Geophysical Research Letters, 2013, 40(6): 1065-1068.

DOI：10.1002/grl.50284

We present a new method for estimating the length and maximum thickness (aperture) of a dike from the observed opening at one dike tip. We apply the method to 15 arrested non-feeder dikes (where the upper tip is known, the lower tip unknown) in the caldera walls of Miyake-jima, Japan, to estimate the length-thickness ratio, as well as the magma overpressure and fracture toughness. The calculated length-thickness ratio ranges from 61 to 246, with an average of 136. The ratios are low because the dikes are emplaced close to the surface in comparatively compliant (soft) rocks. Using these ratios and the appropriate elastic constants, the calculated magmatic overpressures of the dikes are between 2.3 and 8.9MPa, and the stress intensity factors between 38 and 117 MPam(1/2). All these values are within the range of typical in situ estimates, supporting the validity of this new method.

• 出版日期2013-3-28