Notes: The Mazhan Basin, Shandong Province, China, is located between the main faults, F3 and F4, of the Tan-Lu Fault Zone. It is an elongated basin more than 60 km in length and 8 km in width and contains a series of typical continental sediments (the Upper Cretaceous Wangshi Group). This series was divided into three sedimentary facies associations: conglomerate facies association; sandstone facies association of alluvial fan to lake margin environment; and siltstone facies association of lacustrine origins. Their zonal distribution pattern may represent a contemporaneous heterotopic facies due to a lateral facies change from margins to axis of the basin. Their stratigraphic sequence becomes younger northward along the boundary faults. This suggests that the depocenter of the fan–lake system tends to migrate northward along F3. From the asymmetric features (i.e. basin shape, lithofacies distribution, facies change) the Mazhan Basin can be explained by progressive subsidence at the Tangwu releasing bend of F3 with sinistral strike–slip movement. Judging from the fission track (FT) ages from the Wangshi Group, it was concluded that a sinistral strike–slip movement along the main fault, F3 of the Tan-Lu Fault in Shandong, has lasted until the Late Cretaceous. Its displacement is estimated to be larger than the migrated distance, 60 km, of the depocenter of the Mazhan Basin.

Notes: Abstract Drilling was carried out to penetrate the Nojima Fault where the surface rupture occurred associated with the 1995 Hyogo-ken Nanbu earthquake. Two 500 m boreholes were successfully drilled through the fault zone at a depth of 389.4 m. The drilling data show that the relative uplift of the south-east side of the Nojima Fault (south-west segment) was approximately 230 m. The Nojima branch fault, which branches from the Nojima Fault, is inferred to extend to the Asano Fault. From the structural contour map of basal unconformity of the Kobe Group, the vertical component of displacement of the Nojima branch–Asano Fault is estimated to be 260–310 m. Because the vertical component of displacement on the Nojima Fault of the north-east segment is a total of those of the Nojima Fault of the south-west segment and of the Nojima branch–Asano Fault, it is estimated to total to 490–540 m. From this, the average vertical component of the slip rate on the Nojima Fault is estimated to be 0.4–0.45 m/103 years for the past 1.2 million years.

Notes: Field surveys and trench excavation investigations revealed that there were at least four large seismic events produced by slips on the Gosukebashi fault in the Holocene in the southeastern Rokko Mountains of Japan. The characteristics of deformed topographies and three-dimensionally excavated exposures show that this fault is a right-lateral strike–slip fault having an average slip rate of 1.0 mm/year, with a reverse displacement component. The principle indicators of past faulting events are: (i) termination of secondary faults; (ii) sedimentary deposits related to faulting; and (iii) injection veins of fault gouge related to seismic faulting in the fractured zone. Radiocarbon dates indicate that the events occurred pre-1660 BC, 1660 BC–220 AD, from ∼ 30–220 to 600 AD and 15th century AD. The youngest event is probably associated with the large 1596 AD Keicho-Fushimi earthquake which occurred in the area around Kyoto and Kobe Cities. The second younger event is probably correlated with the 416 AD Yamato earthquake, which is the oldest historic earthquake in Japanese historic records. The results of trench surveys show that the horizontal displacement produced by an individual event is ∼ 1.5 m, and the recurrence of seismic event intervals is ∼ 1200 years in the Gosukebashi fault.

Notes: Abstract Cataclastic rocks found in the Disaster Prevention Research Institute, Kyoto University (DPRI) 500 m drill core and outcrops along the Nojima Fault zone on Awaji Island, southwest Japan, were examined at mesoscopic and microscopic scales. The damaged zone of this fault in granitic rocks, observed on the southeast side of the fault, is 50–60 m wide and is composed of fractured host rocks and cataclastic rocks including cataclasite, fault breccia, and fault gouge. The fault breccia and gouge of small scales are scattered in the damaged zone. Fault core (zone of extremely concentrated shearing deformation along a fault) consists of fault gouge measuring several tens to approximately 150 mm in width, as recognized both in the drill core and at outcrops of the Nojima Fault along which surface ruptures formed during the 1995 Kobe earthquake. Fault breccia, measuring a few meters wide, has developed pervasively in the damaged zone, just next to the fault core. Pseudotachylyte has been found interlayered with fault gouge within the fault core only at outcrops at Hirabarashi, not in the DPRI 500 m core. Petrological studies and powder X-ray diffraction analysis show that the pseudotachylyte and fault gouge are composed mainly of fine-grained angular clasts of the host granitic rocks, suggesting the pseudotachylyte is of ‘crush origin’. Foliated cataclasite is characterized by the preferred orientation of elongated biotite clasts and granular aggregates of quartz and feldspar clasts, and by the development of cataclastic shear bands. Unlike cataclastically deformed quartz and feldspar in the cataclasite, biotite in the foliated cataclasite shows combinations of brittle and plastic deformation, such as biotite ‘fish’, cleavage steps, bending and kinking. These textures suggest that the foliated cataclasite formed at a deeper level than the cataclasite, fault breccia and gouge, possibly before the Quaternary period during which the Nojima Fault has moved as a dextral strike–slip fault with some reverse movement resulting in the uplifting of Awaji Island. Examination of fault rocks from surface outcrops can yield similar results to those obtained from drill cores with regard to the internal structures of a fault zone.

Notes: Abstract This paper describes the results of petrographical and meso- to microstructural observations of brittle fault rocks in cores obtained by drilling through the Nojima Fault at a drilling depth of 389.52 m. The zonation of deformation and alteration in the central zone of the fault is clearly seen in cores of granite from the hanging wall, in the following order: (i) host rock, which is characterized by some intragranular microcracks and in situ alteration of mafic minerals and feldspars; (ii) weakly deformed and altered rocks, which are characterized by transgranular cracks and the dissolution of mafic minerals, and by the precipitation of zeolites and iron hydroxide materials; (iii) random fabric fault breccia, which is characterized by fragmentation, by anastomosing networks of transgranular cracks, and by the precipitation of zeolites and iron hydroxide materials; and (iv) fault gouge, which is characterized by the precipitation of smectite and localized cataclastic flow. This zonation implies that the fault has been weakened gradually by fluid-related fracturing over time. In the footwall, a gouge layer measuring only 15 mm thick is present just below the surface of the Nojima Fault. These observations are the basis for a model of fluid behavior along the Nojima Fault. The model invokes the percolation of meteoric fluids through cracks in the hanging wall fault zone during interseismic periods, resulting in chemical reactions in the fault gouge layer to form smectite. The low permeability clay-rich gouge layer sealed the footwall. The fault gouge was brecciated during coseismic or postseismic periods, breaking the seal and allowing fluids to readily flow into the footwall, thus causing a slight alteration. Chemical reactions between fluids and the fault breccia and gouge generated new fault gouge, which resealed the footwall, resulting in a low fluid condition in the footwall during interseismic periods.