Radiation from a strike-slip fault

abstract Huygens' principle for elastodynamics has been applied to the problem of the radiation resulting from the introduction of a tear fault of finite length into an otherwise homogeneous medium. The fault has the following properties: (1) it is a surface across which the normal stresses vanish; (2) it has a rectangular shape with one dimension increasing at a constant rate in the direction of faulting; (3) the times of initiation and termination of the fault are both finite. The relative displacement on opposite sides of the fault is prescribed to be a step function of time. This configuration may be imaged in the earth's surface by symmetry, so that the problem is reducible to that of a propagating strike-slip fault of finite length in an infinite elastic medium. The observed events are the P and S waves from the two ends of the fault. Simplified “first motion” responses are computed and compared with solutions derived from the usual theory of force couples.

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Pipeline Design Method Against Large Displacement of Strike-Slip Fault

Volume 8: Seismic Engineering ◽

10.1115/pvp2016-63699 ◽

2016 ◽

Author(s):

Keita Oda ◽

Takahiro Ishihara ◽

Masakatsu Miyajima

Keyword(s):

Elastic Limit ◽

Design Method ◽

Fem Analysis ◽

Relative Displacement ◽

Strike Slip ◽

Strike Slip Fault ◽

Large Displacement ◽

Pipeline System ◽

Tensile Direction ◽

Fault Displacement

This study proposes a method for designing a water pipeline system against fault displacement by incorporating earthquake resistant ductile iron pipes (ERDIPs). An ERDIP pipeline is capable of absorb the large ground displacements that occur during severe earthquakes by movement of its joint (expansion, contraction and deflection) and the use of the joint locking system. Existing ERDIP pipelines have been exposed to several severe earthquakes such as the 1995 Kobe Earthquake and the 2011 Great East Japan Earthquake, and there has been no documentation of their failure in the last 40 years. In the case of a pipeline that crosses a fault, there is the possibility of the occurrence of a local relative displacement between the pipeline and the ground. It is known that an ERDIP pipeline withstands a fault of axial compression direction by past our study. Hence, this present study was targeted at developing a method for designing an ERDIP pipeline that is capable of withstanding a strike-slip fault of axial tensile direction for a pipeline. This was done by FEM analysis wherein the ERDIPs and spring elements were used to model the soil and ERDIP joints. An ERDIP pipeline can accommodate a fault displacement of about 2 m by joint expansion/contraction and deflection, while maintaining the stress in the pipeline within the elastic limit. However, additional countermeasure is required when the fault displacement exceeds 2 m because such could stress the pipeline beyond the elastic limit. The use of large displacement absorption unit is an effective countermeasure for displacements exceeding 2 m. The expansion/contraction capacity of a unit is 10 times that of an ERDIP joint and it is able to absorb a locally-concentrated axial displacement of the pipeline. It was confirmed in the present study that an ERDIP pipeline with large displacement absorption unit, referred to as a large displacement absorption system, could accommodate fault displacement in excess of 2 m within the elastic stress range of the pipeline.

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