A recent deep earthquake doublet in light of long-term evolution of Nazca subduction.

Earthquake faulting at ~600 km depth remains puzzling. Here we present a new kinematic interpretation of two Mw7.6 earthquakes of November 24, 2015. In contrast to teleseismic analysis of this doublet, we use regional seismic data providing robust two-point source models, further validated by regional back-projection and rupture-stop analysis. The doublet represents segmented rupture of a ∼30-year gap in a narrow, deep fault zone, fully consistent with the stress field derived from neighbouring 1976-2015 earthquakes. Seismic observations are interpreted using a geodynamic model of regional subduction, incorporating realistic rheology and major phase transitions, yielding a model slab that is nearly vertical in the deep-earthquake zone but stagnant below 660 km, consistent with tomographic imaging. Geodynamically modelled stresses match the seismically inferred stress field, where the steeply down-dip orientation of compressive stress axes at ∼600 km arises from combined viscous and buoyant forces resisting slab penetration into the lower mantle and deformation associated with slab buckling and stagnation. Observed fault-rupture geometry, demonstrated likelihood of seismic triggering, and high model temperatures in young subducted lithosphere, together favour nanometric crystallisation (and associated grain-boundary sliding) attending high-pressure dehydration as a likely seismogenic mechanism, unless a segment of much older lithosphere is present at depth.

Language and the developing child: Pivotal ideas of Katrina de Hirsch.

This paper considers the contributions of Katrina de Hirsch to the understanding of developmental language disabilities. It focuses on subjects that especially interested her: neurophysiological immaturity, the cluttering syndrome, the prediction of reading failure, intervention, and normal language development.

Prediction: A six-year follow-up.

The prereading and reading performance of a group of 370 predominantly Hispanic, bilingual public school children was followed for six years. The aim of the study was to compare the factorial make-up and predictive validity of tests used in the current research with findings from a previous study. The early study had followed the children from the end of their kindergarten year until the end of second grade. For purposes of the present study a 13-test predictor battery was administered to the children at the beginning of their first-grade year. This battery included a number of measures used in the early study, among them a 5-test Screening Index developed in the course of that study. Records were obtained of the follow-up children's 2nd, 3rd, 4th, 5th, and 6th grade reading test scores. Factor analysis of the pool of 13 predictor tests showed a two-cluster battery structure. These clusters closely resembled two of the four factors defined in the early study. As used with the group of bilingual children, the Screening Index misclassified many of the failing readers, as well as others who went ahead to read at grade level. The Screening Index quite accurately identified, across grades, children who eventually read well. A number of predictor tests administered at beginning of first grade continued to show significant correlations with reading at all grade levels. The consistent contribution of the predictor tests with reading points to their continuing usefulness as a point of departure for assessing children's readiness to read.