Abstract This paper traces the growth of seismology in the western United States, giving emphasis to geological connections. Pre-instrumental foundations of a science of earthquakes were laid late last century by geologists, especially G. K. Gilbert. These early studies were based largely on Quaternary tectonic structural features evident in the west. The 1906 San Francisco earthquake resulted in a tremendous increase in seismological research and knowledge, including H. F. Reid’s “elastic rebound” fault theory of the seismic source, theses on seismic hazards, prediction, seismometry, and other related topics. Significant growth of seismographic networks in California under the auspices of the University of California, Berkeley, and the California Institute of Technology, led to many geologically valuable results on such issues as seismic activity, tectonic patterns, and focal mechanisms. This discussion covers the period up to about 1960.

Abstract This review of the role of the mantle lithosphere in plate tectonic processes collates a wide range of recent studies from seismology and numerical modelling. A continually growing catalogue of deep geophysical imaging has illuminated the mantle lithosphere and generated new interpretations of how the lithosphere evolves. We review current ideas about the role of continental mantle lithosphere in plate tectonic processes. Evidence seems to be growing that scarring in the continental mantle lithosphere is ubiquitous, which implies a reassessment of the widely held view that it is the inheritance of crustal structure only (rather than the lithosphere as a whole) that is most important in the conventional theory of plate tectonics (e.g. the Wilson cycle). Recent studies have interpreted mantle lithosphere heterogeneities to be pre-existing structures and, as such, linked to the Wilson cycle and inheritance. We consider the current fundamental questions in the role of the mantle lithosphere in causing tectonic deformation, reviewing recent results and highlighting the potential of the deep lithosphere in infiltrating every aspect of plate tectonics processes.

Abstract 1. This paper treats of the propagation of vibrations over the surface of a “semi-infinite” isotropic elastic solid, i.e., a solid bounded only by a plane. For purposes of description this plane may be conceived as horizontal, and the solid as lying below it, although gravity is not specially taken into account. The vibrations are supposed due to an arbitrary application of force at a point. In the problem most fully discussed this force consists of an impulse applied vertically to the surface; but some other cases, including that of an internal source of disturbance, are also (more briefly) considered. Owing to the complexity of the problem, it has been thought best to concentrate attention on the vibrations as they manifest themselves at the free surface. The modifications which the latter introduces into the character of the waves propagated into the interior of the solid are accordingly not examined minutely. The investigation may perhaps claim some interest on theoretical grounds, and also in relation to the phenomena of earthquakes. Writers on seismology have naturally endeavoured from time to time to interpret the phenomena, at all events in their broader features, by the light of elastic theory. Most of these attempts have been based on the laws of wave-propagation in an unlimited medium, as developed by G reen and S tokes ; but Lord R ayleigh ’S discovery of a special type of surface-waves has made it evident that the influence of the free surface in modifying the character of the vibrations is more definite and

The plate tectonic processes, or “plate,” model for the genesis of melting anomalies (“hotspots”) attributes them to shallow-sourced phenomena related to plate tectonics. It postulates that volcanism occurs where the lithosphere is in extension, and that the volume of melt produced is related primarily to the fertility of the source material tapped. This model is supported in general by the observation that most present-day “hotspots” erupt either on or near spreading ridges or in continental rift zones and intraplate regions observed or predicted to be extending. Ocean island basalt-like geochemistry is evidence for source fertility at productive melting anomalies. Plate tectonics involves a rich diversity of processes, and as a result, the plate model is in harmony with many characteristics of the global melting-anomaly constellation that have tended to be underemphasized. The melting anomalies that have been classified as “hotspots” and “hotspot tracks” exhibit extreme variability. This variability suggests that a “one size fits all” model to explain them, such as the classical plume model, is inappropriate, and that local context is important. Associated vertical motion may comprise pre-, peri-, or post-emplacement uplift or subsidence. The total volume erupted ranges from trivial in the case of minor seamount chains to ∼10 8 km 3 for the proposed composite Ontong Java–Manihiki–Hikurangi plateau. Time progressions along chains may be extremely regular or absent. Several avenues of testing of the hypothesis are being explored and are stimulating an unprecedented and healthy degree of critical debate regarding the results. Determining seismologically the physical conditions beneath melting anomalies is challenging because of problems of resolution and interpretation of velocity anomalies in terms of medium properties. Petrological approaches to determining source temperature and composition are controversial and still under development. Modeling the heat budget in large igneous provinces requires knowledge of the volume and time scale of emplacement, which is often poorly known. Although ocean island basalt–type geochemistry is generally agreed to be derived from recycled near-surface materials, the specifics are still disputed. Examples are discussed from the Atlantic and Pacific oceans, which show much commonality. Each ocean hosts a single, currently forming, major tholeiitic province (Iceland and Hawaii). Both of these comprise large igneous provinces that are forming late in the sequences of associated volcanism rather than at their beginnings. Each ocean contains several melting anomalies on or near spreading ridges, both time- and non-time-progressive linear volcanic chains of various lengths, and regions of scattered volcanism several hundred kilometers broad. Many continental large igneous provinces lie on the edges of continents and clearly formed in association with continental breakup. Other volcanism is associated with extension in rift valleys, back-arc regions, or above sites of slab tearing or break-off. Specific plate models have been developed for some melting anomalies, but others still await detailed application of the theory. The subject is currently developing rapidly and poses a rich array of crucial but challenging questions that need to be addressed.

Abstract Love was one of four children and the second son of John Henry Love, a surgeon of Somersetshire. He was educated at Wolverhampton Grammar School, and his subsequent career owed much to his mathematical master, the Reverend Henry Williams. He entered St. John’s College, Cambridge, in 1882. He was a fellow of St. John’s College from 1886 to 1889 and held the Sedleian chair of natural philosophy at Oxford from 1899 on. He was elected a fellow of the Royal Society of London in 1894. Love was secretary of the London Mathematical Society for fifteen years and president in 1912–1913. He was noted as a quiet, unassuming, brilliant scholar, with a logical and superbly tidy mind. He liked traveling, was interested in music, and played croquet. He never married; a sister, Blanche, kept house for him. Love’s principal research interests were the theory of deformable media, both fluid and solid, and theoretical geophysics. He also contributed to the theory of electric waves and ballistics, and published books on theoretical mechanics and the calculus. Love’s first great work, A Treatise on the Mathematical Theory of Elasticity, appeared in two volumes in 1892–1893. A second edition, largely rewritten, appeared in 1906 and was followed by further editions in 1920 and 1927. This treatise, translated into several foreign languages, served as the world’s standard source on the subject for nearly half a century. It is a masterpiece of exposition and stands as a classic in the literature of mathematical physics. It continues to