Present‐day plate motions

Abstract

A data set comprising 110 spreading rates, 78 transform fault azimuths, and 142 earthquake slip vectors has been inverted to yield a new instantaneous plate motion model, designated Relative Motion 2 (RM2). The model represents a considerable improvement over our previous estimate, RM1 [Minster et al., 1974]. The mean averaging interval for the spreading rate data has been reduced to less than 3 m.y. A detailed comparison of RM2 with angular velocity vectors which best fit the data along individual plate boundaries indicates that RM2 performs close to optimally in most regions, with several notable exceptions. The model systematically misfits data along the India‐Antarctica and Pacific‐India plate boundaries. We hypothesize that these discrepancies are manifestations of internal deformation within the Indian plate; the data are compatible with northwest‐southeast compression across the Ninetyeast Ridge at a rate of about 1 cm/yr. RM2 also fails to satisfy the east‐west trending transform fault azimuths observed in the French‐American Mid‐Ocean Undersea Study area, which is shown to be a consequence of closure constraints about the Azores triple junction. Slow movement between North and South America is required by the data set, although the angular velocity vector describing this motion remains poorly constrained. The existence of a Bering plate, postulated in our previous study, is not necessary if we accept the proposal of Engdahl and others that the Aleutian slip vector data are biased by slab effects. Absolute motion models are derived from several kinematical hypotheses and compared with the data from hot spot traces younger than 10 m.y. Although some of the models are inconsistent with the Wilson‐Morgan hypothesis, the overall resolving power of the hot spot data is poor, and the directions of absolute motion for the several slower‐moving plates are not usefully constrained.

Seismic recurrence intervals and timing of aseismic subduction inferred from emerged corals and reefs of the Central Vanuatu (New Hebrides) Frontal Arc

“…Later, using the model of Savage and Gu [1985] and a fault dip of so•, Taylor et al [1987] required only 2.0 m of slip. In SM, the only known large event in the vicinity had a While there are uncertainties in these estimates of the fraction of seismic slip, the authors of the present study believe that it is possible, but not very likely, that they are large enough to nullify our conclusion that the seismic slip rate is considerably smaller than the plate convergence rates reported by Minster and Jordan [1978] and Gordon et al [1988].…”

“…If our analysis of seismic moment is correct and if the plates presently converge at approximately the rate reported by Minster and Jordan [1978], our principal conclusion is that most of the slip is aseismic. Indeed, our calculations indicate that the earthquake moments represent less than one-third to one-tenth of the plate convergence since 1920.…”

“…We propose Minimum and maximum estimates of seismic moment are smallest and largest moments reported by E [Ebel, 1980], C&l [Chinn and Isacks, 1983], or S which is determined from available reported surface wave magnitudes using the relation of Hanks and . When earthquake sequence includes more than one event, the moment values in the [Minster and Jordan, 1978] does not include the expected contribution from back arc spreading on the Fiji plateau [e.g., Falvey, 1975]. Boundaries between frontal arc segments are taken from Taylor et al [1980Taylor et al [ , 1987 and are supported by independent studies including Ebel [1980].…”

Heat flow at the spreading centers of the Guaymas Basin, Gulf of California

“…Approximately 240 km long by 60 krn wide, it contains a distinct central depression just over 2000 m deep, divided into two troughs that are offset consistent with right lateral North America-Pacific plate mouon. The North America-Pacific pole of rotation in northeast Canada at 48.8°N, 73.9°W [Minster and Jordan, 1978) implies that the Guaymas basin spreading rate does not differ significantly from that measured on the East Pacific Rise at the mouth of the Gulf of California, 3. 1-cm/yr half rate [Larson, 1972].…”

Seismic and non-seismic influences on coastal change in Alaska--Fieldtrip guide and conference abstracts, 5th International Conference of IGCP 588

“…4.2.1). In this area the convergence rate between the Pacific and North American plates is about 5.5 cm/yr in a N18°W direction (Minster and Jordan 1978). The M 9.2 1964 Alaska earthquake was the greatest seismotectonic event of the 20th century in terms of the known surface area affected by crustal deformation.…”