Sandbox modeling is used to study the deformation of accretionary wedges caused by the subduction of oceanic ridges. The first experiment incorporates a massive ridge within a sand wedge. The wedge thickens and shortens when the forward propagation f the basal decollement ceases. The wedge thickening results in taper change, reactivation of preexisting thrusts, and retreat of the frontal part o...

Seismological data from recent subduction earthquakes suggest that megathrust earthquakes induce transient stress changes in the upper plate that shift accretionary wedges into an unstable state. These stress changes have, however, never been linked to geological structures preserved in fossil accretionary complexes. The importance of coseismically induced wedge failure has therefore remained l...

[1] We expand the theory of critically tapered Coulomb wedge for accretionary prisms by considering stress changes in subduction earthquake cycles. Building on the Coulomb plasticity of the classical theory, we assume an elastic–perfectly Coulomb plastic rheology and derive exact stress solutions for stable and critical wedges. The new theory postulates that the actively deforming, most seaward...

We evaluated the influence of the trench-parallel component of plate motion on the active fault system within the Nankai accretionary wedge from reflection seismic profiles, high-resolution seafloor bathymetry, and deep-towed sub-bottom profiles. Our study demonstrated that a large portion of the trench-parallel component of oblique plate subduction is released by strike-slip motion along a fau...

To gain a better understanding of the mechanical and chemical behavior of accretion and underplating and tectonic erosion and to determine how deformation and dewatering are distributed throughout an accretionary prism, it is essential to establish the flow pattern of materials through subduction systems. Leg 170 consists of a program of drilling at four primary sites (proposed Sites CR-1 throu...

The June 15, 1896 Sanriku earthquake generated devastating tsunamis with the maximum run-up of 25 m and caused the worst tsunami disaster in the history of Japan, despite its moderate surface wave magnitude (Ms=7.2) and weak seismic intensity. This is a typical tsunami earthquake, which generates anomalously larger tsunamis than expected from its seismic waves. Previously proposed mechanisms of...

Mud volcanism was initiated when overpressured muds rose through the Mediterranean Ridge accretionary prism. Early mud volcanism was marked by eruption of coarse clastic sediments forming small cones of debris flow deposits and turbidites, followed by eruption of large volumes of clast-rich matrix-supported debris flows. Eruption was accompanied by progressive subsidence to form moat-like featu...

[1] In this study, we used porosity to assess the compaction state of the Nankai accretionary wedge sediments and any implications for stress and pore pressure. However, hydrous minerals affect porosity measurements, and accounting for them is essential toward defining the interstitial porosity truly representative of the compaction state. The water content of sediments was measured in core sam...

A number of observations indicate that an upper stability transition occurs along well-developed faults, such as the San Andreas, as a result of unconsolidated gouge within shallow regions of these faults. These observations include the depth distribution of seismicity along faults with and without well-developed gouge zones, correlations between seismicity and shallow crustal structure, and mo...