著者

岸尾 政弘 山川 宜男

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.22, no.3, pp.219-234, 1969-11-30 (Released:2010-03-11)

参考文献数

27

被引用文献数

1 1

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The precision and accuracy of locations of hypocenters of the earthquake off Tokachi of 16 May 1968 and its aftershocks are discussed mainly based on the comparison between both data determined by JMA and USCGS.USCGS epicenters are generally on the continental side of JMA epicenters. The average distance of both JMA and USCGS epicenters of each shock is 26.4km. However there are systematic differences between the JMA-USCGS epicenter deviation of aftershocks north of the mainshock and those of aftershocks south of the mainshock. The USCGS epicenters of northern aftershocks are deviated to north-west direction from the JMA epicenter while USCGS epicenters of southern aftershocks are deviated to west direction from the JMA epicenter.Focal depths of USCGS hypocenters are a little deeper than those of JMA hypocenters. 40% of JMA hypocenters and 80% of USCGS hypocenters are located in the depth of 30-40km which correspond to the top layer of the mantle.Slight differences of b-values in the magnitude-frequency relations are observed among aftershockes in the northern area (around the epicenter of the greatest aftershock), those in the middle area (around the epicenter of the main shock) and those in the southern area (around the epicenter of the second greatest aftershock).The geophysical significance of the above results is briefly discussed.

著者

山川 宜男

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.8, no.2, pp.84-98, 1955-10-20 (Released:2010-03-11)

参考文献数

7

被引用文献数

18

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Japanese seismologists succeeded in explaining the push-pull distribution of the initial motion of earthquakes by assuming two types stress distribution on the sphere which covers the hypocenter. Type A is the combination of hydrostatic pressure and pressure with distribution expressed in spherical harmonic P2(cosθ). Type B is the distribution of pressure expressed in P21(cosθ)cosφ. Generally the polar axis of these spherical harmonics does not coincide with vertical axis. On this point, Y. Sato obtained the formulae which express the transformation of the spherical harmonics by the rotation of coordinate system. According to his result, P2(cosθ0)=P2(cosθ)(1/4+3/4cos2χ)+P21(cosθ)cos(φ-φ)(1/2sin2χ)+P22(cosθ)cos2(φ-φ)(1/8-1/8cos2χ)P21(cosθ0)cosφ0=[sinφA21-cosφB21]where A21=P21(cosθ)sin(φ-φ)cosχ+P22(cosθ)sin2(φ-φ)(1/2sinχ)B21=P2(cosθ)(3/2sin2χ)-P21(cosθ)cos(φ-φ)cos2χ-P22(cosθ)cos2(φ-φ)(1/4sin2χ)where (φ, φ, χ) is Euler angles which express the rotation of the coordinate.In this paper, we calculated the strain produced in a semi-infinite elastic solid when hydrostatic pressure and pressure with distribution expressed in spherical harmonics P2(cosθ), P21(cosθ)cosφ, P22(cosθ)cos2φ were applied at the interior spherical cavity.The deformations expressed in cylindrical coordinate (R, φ, z) at the surface of semiinfinite elastic solid are as follows:—(1) The case in which hydrostatic pressure -P is appliedUR=3a3P/4μR/(f2+R2)3/2, Uφ=0, Uz=-3a3P/4μf/(f2+R2)3/2(2) The case of -PP2(cosθ)UR=3a3P/46μ[-5P/(f+R23/2)+18f2R/(f2+R2)5/2], Uφ=0, Uz=-3a3P/46μ[-5f/(f2+R23/2)+18f3/(f2+R2)5/2](3) The case of -PP21(cosθ)cosφUR=54a3P/23μcosφ[-f((f2+R2)3/2+f3(f2+R2)5/2], Uφ45a5P/184μsinφf(R2+f2)5/2, Uz=45a5P/184μsinφf(R2+f2)5/2(4) The case of -PP22(cosθ)cos2φUR=9a3P/23μcos2φ[4f/R3-4f2/R3(R2+f2)1/2+5R(f2+R2)3/2-2f2/R(R2+f2)3/2-6f2R