We present data and models for the present-day stress and strain pattern in the Pannonian Basin and surrounding East Alpine–Dinaric orogens. Formation of the Pannonian Basin within the Alpine mountain belt started in the early Miocene, whereas its compressional reactivation has been taking place since late Pliocene–Quaternary time. Basin inversion is related to changes in the stress field from a state of tension during basin formation in the Miocene to a state of compression resulting from the convergence between the Adria microplate and the European plate. Seismicity indicates that deformation is mainly concentrated along Adria's boundaries where pure contraction (thrusting in Friuli and the southeastern Dinarides), often in combination with transform faulting (dextral transpression in the central Dinarides), is predominant. Tectonic stresses and deformation are transferred into the Pannonian Basin, resulting in a complex pattern of ongoing tectonic activity. From the margin of Adria toward the interior of the Pannonian Basin, the dominant style of deformation gradually changes from pure contraction, through transpression, to strike-slip faulting. Shortening in the basin system, documented by earthquake focal mechanisms, global positioning system (GPS) data, and the neotectonic habitat, has led to considerable seismotectonic activity and folding of the lithosphere. The state of recent stress and deformation in the Pannonian Basin is governed by the interaction of plate-boundary and intraplate forces, which include the counterclockwise rotation and N-NE–directed indentation of the Adria microplate (“Adria-push”) as the dominant source of compression, in combination with buoyancy forces associated with differential topography and lithospheric heterogeneities.

ABSTRACT The Northern Channel Islands demonstrate pervasive Quaternary deformation, including faulting, regional warping, and localized folding. Field mapping on Santa Cruz Island, interpretation of seismicreflection profiles north of the island, measurement of fault-zone striations, and study of uplifted and deformed coastal terraces show which structures have been active in the late Quaternary and the pattern and rates of deformation during that time. The Santa Cruz Island fault is the largest and most active ground-rupturing fault on the island. The fault is predominantly left-lateral, although striations and displaced landforms demonstrate that it has a smaller, but significant component of reverse slip. The Poso Beach fault is an active reverse structure that cuts a 125 ka coastal terrace on southwest Santa Cruz Island. Other major faults include the “south branch” of the Santa Cruz Island fault, the Potato Harbor fault, and “Fault C”, but conclusive evidence of late Quaternary slip on these faults is lacking at this time. In addition to brittle deformation, regional warping is recorded by deformation of Pleistocene coastal terraces and progressive submergence and tilting on the island’s northern continental shelf. North of the Santa Cruz Island fault, warping takes the form of subsidence of the shelf and uplift of the island, with uplift reaching a maximum near the fault. On the south half of the island, deformation consists of a broad, low-amplitude south tilt, upon which localized folding associated with the Poso Beach fault and the Christi anticline is superimposed. These secondary folds, as well as southeast-striking right-lateral faults near Valley Anchorage, probably represent local accommodation of right-lateral structures of the California Borderland as they meet the east-west-trending western Transverse Ranges to the north. Overall, the pattern of late Quaternary deformation on Santa Cruz Island is consistent with a model in which the island, and probably the entire Northern Channel Islands chain, is part of a regional anticline, the north limb of which is progressively tilting above a concave-up listric thrust fault.