**Author details**

**6. Conclusion**

actual structures.

We simply reviewed on dislocation modeling and on its applications to geological problems

**Figure 12.** Two-dimensional gravity modelling along D-D' profile in Figure 7. Blue circle shows measured Bouguer gravity anomalies and red solid line shows calculated values. Bottom figure shows the density structure. Density con‐ trasts of sedimentary layer-crust and crust-mantle were assumed to be -300 kg/m3 and -500 kg/m3, respectively.

**1.** When discussing the essential aspects of tectonics, simply from a distribution pattern of structures caused by fault motions, the dislocation modeling was a very useful tool and should be used with an assumption of a high Poisson's ratio. However, it is difficult to directly compare the displacement amounts between the modeled structures and the

**2.** It is useful to superimpose analytical solutions for different fault parameters on a single fault, in order to introduce the history of fault activity into the numerical model.

We then employed the suggested dislocation modeling technique for the restoration modeling of sedimentary basins formed from 48 Ma to 12 Ma (located in central Hokkaido, Japan), and evaluated the fault types (lateral faulting or reverse faulting). As a result it was found that: **3.** Sedimentary basins that were formed from 48 to 12 Ma in central Hokkaido can be explained by the formation of pull-apart basins, due to right lateral motions before 13 Ma, and by reverse motions of the Hidaka-North fault zone and the Hidaka-South fault zone after 13 Ma. Although this makes us expect a significant change in the regional tectonic

(including the disadvantages of the model), and make the following two points.

296 Mechanism of Sedimentary Basin Formation - Multidisciplinary Approach on Active Plate Margins

Shigekazu Kusumoto1 , Yasuto Itoh2 , Osamu Takano3 and Machiko Tamaki4

1 Graduate School of Science and Technology for Research, University of Toyama, Japan

2 Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Japan

3 JAPEX Research Center, Japan Petroleum Exploration Co. Ltd., Japan

4 Japan Oil Engineering Co. Ltd., Japan
