Journal of Physics of the Earth
Online ISSN : 1884-2305
Print ISSN : 0022-3743
ISSN-L : 0022-3743
Volume 42, Issue 3
Displaying 1-4 of 4 articles from this issue
  • Sarva Jit Singh, Sunita Rani
    1994 Volume 42 Issue 3 Pages 197-220
    Published: 1994
    Released on J-STAGE: April 30, 2009
    JOURNAL FREE ACCESS
    To model the coseismic and postseismic lithospheric deformations associated with faulting at a transform plate boundary, the problem of a long inclined strike-slip fault in a layer overlying a uniform half-space is discussed. Closed-form expressions for the static displacements and stresses are obtained when the two media are elastic. These expressions are used to study the effect of the source location and the dip of the fault on the surface deformation. The correspondence principle of linear viscoelasticity is used to obtain the quasi-static field when the layer is elastic and the half-space Maxwell viscoelastic. The coseismic field is modeled by the static response and the postseismic field is modeled by the quasi-static response minus the static response. The variation of the coseismic and postseismic surface displacement and shear stress with the distance from an inclined fault is studied for four source locations: a surface-breaking fault and three buried faults. Both the source location and the dip of the fault are found to influence the deformation field significantly. Contours of constant postseismic displacement and stresses on the distance-time grid are obtained. These contours are useful in examining the spatial and temporal dependence of the displacement and stress fields. It is found that while the nodal lines for the postseismic displacement are independent of time, the nodal lines for the postseismic shear stresses move away from the fault with time after the earthquake.
    Download PDF (1520K)
  • Yasunori Tohjima, George Igarashi, Hiroshi Wakita
    1994 Volume 42 Issue 3 Pages 221-235
    Published: 1994
    Released on J-STAGE: April 30, 2009
    JOURNAL FREE ACCESS
    Precise measurement of the flow rate of groundwater was started in August 1991 at an observation well (KSM) in the eastern part of Fukushima Prefecture, Northeast Japan. This well, located right on the Futaba fault, has shown systematically earthquake-related changes in the radon concentration of the groundwater. Although anomalous changes in the flow rate associated with earthquakes have not been observed, the flow rate showed fluctuations responding to Earth tides and atmospheric loading. The phase of the response to the theoretical tidal strain advanced and the tidal strain sensitivity to the semidiurnal constituents are larger than that to the diurnal constituents. These responses can be explained by groundwater leakage from the aquifer, which is consistent with the fractured crustal structure around the strainer position.
    Download PDF (1431K)
  • Hiroki Miyamachi
    1994 Volume 42 Issue 3 Pages 237-260
    Published: 1994
    Released on J-STAGE: April 30, 2009
    JOURNAL FREE ACCESS
    We have developed an inverse method to estimate a three-dimensional seismic wave velocity structure using seismic arrival time data obtained from local earthquakes. The method is characterized by a simultaneous determination of a two-dimensional depth distribution of a velocity boundary, a three-dimensional velocity distribution, station corrections and hypocenters. The depth distributions of velocity boundaries and the distributions of the slowness perturbations for P and S waves are modeled by power series of latitude, longitude, and depth, This representation of the three-dimensional seismic structure is advantageous not only in reducing the number of unknown parameters, but also in analytically evaluating the boundary depths, velocities, and partial derivatives of travel times with respect to the unknown parameters. Ray tra-jectories connected between hypocenters and stations are determined by the so-called shooting method for ray tracing scheme under a simplified velocity distribution with the exact boundary depth distribution. Numerical experiments have proved that our inverse method can successfully estimate the three-dimensional velocity structure.
    Download PDF (2433K)
  • Eiji Mochizuki
    1994 Volume 42 Issue 3 Pages 261-267
    Published: 1994
    Released on J-STAGE: April 30, 2009
    JOURNAL FREE ACCESS
    Download PDF (282K)
feedback
Top