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The young Gulf of Corinth rift in central Greece is an ideal place to study processes occurring during the initiation and early stages of continental extension. At the east end of the 100-km-long E-W rift, Holocene extension on N-dipping faults equates to geodetic extension rates. At the western end, however, estimated extension rates on N-dipping onshore faults account for only ~20 % -40% of the geodetically measured rates (~10-15 mm/ yr). We use high-quality, multichannel, seismic reflection and swath bathymetry data to investigate the tectonics of the western Gulf and quantify the contribution of offshore fault activity toward total-rift extension. Five major offshore faults generate the variable basement topography, and a ca. 0.4-Ma unconformity separates stratigraphy into two main packages. Basin-fill geometry indicates that during the early stages of subsidence of the offshore western Gulf, S-dipping faults were the dominant border-fault structure. This is still the case at the western end of the western Gulf; however, elsewhere, N-dipping faults on the south margin are now relatively more dominant and cause stratigraphy to tilt south. The temporally and spatially varying rift structure contrasts with the simple, consistently N-dipping, border-fault, half-graben geometry of the east Gulf of Corinth. Combined west Gulf offshore and onshore Holocene fault extension rates total 5-14.5 mm/yr, within the range calculated geodetically, and render enhanced slip on a low-angle detachment surface beneath the western Gulf unnecessary. Keywords: Gulf of Corinth, normal fault, seismic reflection, seismic stratigraphy, rift evolution

High-resolution multibeam bathymetry data from the Sumatran subduction zone reveal the regional and local morphology, including small-scale fault-related features and landslides that may be linked to earthquakes in the recent geological past. The accretionary prism is steeply sloped and pervasively eroded, with evidence of unusual landward vergence (seaward fault dip) of the frontal thrusts. Small-scale (5-100 m height) fault scarps, folds, and troughs are common along the seaward edge of the frontal thrust at the deformation front. A model of back-thrust fault slip or bending moment folding during plate-boundary slip, such as during the 2004 M9.2 megathrust earthquake, can explain the position of these features on the seaward fold limb of a seaward-dipping thrust. We infer that in major Sumatran (and other similar settings) plate-boundary earthquakes, coseismic surface rupture may occur at the prism toe. Keywords: subduction zones, Indian Ocean, earthquakes, thrust faults, accretionary prism.

Stonewall Bank is the site of a growing west-verging anticline striking north-northwest on the continental shelf at 44.5 [degrees] N, southwest of Newport, Oregon. To the east are Pliocene-Pleistocene strata of the Newport syncline, onlapping eastward against gently west-dipping late Miocene and older rocks of the Oregon Coast Range. Folding of Stonewall anticline results in fine-grained middle Miocene strata being exposed at the sea floor along the anticlinal crest; rocks as old as Eocene are encountered in the Unocal P-0093-1 Grebe well, drilled at the anticlinal crest. Rates of folding are based on deformation of an unconformity between Pliocene and Miocene strata (PM unconformity) and of a stream channel that crossed Stonewall Bank during the last glacial maximum. The bed length of the unconformity is shortened across the Stonewall anticline and adjacent folds by about 400 m between structures west of Stonewall Bank and the Newport syncline. The PM unconformity has a vertical separation of about 1000 m between the anticline and the first syncline to the west. The horizontal shortening and vertical separation imply that Stonewall anticline is underlain by a blind reverse fault. Retrodeforming the PM unconformity shows that this fault dips 65 [degrees] -70 [degrees] E. A vertical separation of 1000 m on a fault with this dip yields a slip of 1070 - 1080 m along the fault. If folding of the PM unconformity is assumed to have begun 2-3 Ma, this would give a long-term slip rate of 0.4-0.6 mm/yr. If most folding began after deposition of the entire Pliocene-Pleistocene sequence, the slip rate would be 1.0-1.1 mm/yr. Stonewall anticline has arched the late Pleistocene lowstand wave abrasion platform since sea level underwent a rapid rise from 14.5 to 8 ka. This arch is crossed by an antecedent stream channel that is 275-550 m wide and is marked by side drainages and cut banks up to 12 m high. Warping of the platform on the eastern limb of the anticline has back-tilted the stream channel eastward toward its present onshore continuation, the Yaquina River. The platform slopes downward 10-13 m westward from the crest of Stonewall anticline. We estimate that the platform stopped abrading when sea level reached about -40 m at 11-12 ka. Assuming that the west slope of the platform is controlled by the same blind fault that produced the west dip of the PM unconformity, the Holocene slip rate on this fault would be 0.9-1.3 mm/yr, comparable to the long-term slip rate. Rupture of the entire 25 km length of the blind fault with 1 m of slip beneath Stonewall Bank could produce an earthquake with [M.sub.w] = 6.8 [+ or -] 0.25, which would result in peak ground accelerations close to 0.2g on the central Oregon coast.

The continental shelf and upper slope of the Oregon Cascadia margin are underlain by an elongate late Cenozoic forearc basin, correlative to the Eel River basin of northern California. Basin stratigraphy includes a regional late Miocene unconformity that may coincide with a worldwide hiatus ca. 7.5-6 Ma (NH6). The unconformity is angular and probably subaerially eroded on the inner and middle shelf, whereas the seaward correlative disconformity may have been produced by submarine erosion; alternatively, this horizon may be conformable. Tectonic uplift resulting in subaerial erosion may have been driven by a change in Pacific and Juan de Fuca plate motion. A structure contour map of the deformed unconformity and correlated seaward reflector from seismic reflection data clearly outlines deformation into major synclines and uplifted submarine banks. Regional margin-parallel variations in uplift rates of the shelf unconformity show agreement with coastal geodetic rates. The shelf basin is bounded to the west by a north-south-trending outer arc high. Rapid uplift and possible eustatic sea-level fall resulted in the formation of the late Miocene unconformity. Basin subsidence and outer arc high uplift effectively trapped sediments within the basin, which resulted in a relatively starved abyssal floor and narrower Pliocene accretionary wedge, particularly during sea-level highstands. During the Pleistocene, the outer arc high was breached, possibly contributing to Astoria Canyon incision, the primary downslope conduit of Columbia River sediments. This event may have caused a change in sediment provenance on the abyssal plain ca. 1.3-1.4 Ma. Keywords: accretionary wedges, Cascadia subduction zone, forearc basins, neotectonics, submarine fans, unconformity.