We review recent results concerning the rheology of the lithosphere with special attention to the following topics: 1) the flexure of the oceanic lithosphere, 2) deformation of the continental lithosphere resulting from vertical surface loads and forces applied at plate margins, 3) the rheological stratification of the continents, 4) strain localization and shear zone development, and 5) strain-induced crystallographic preferred orientations and anisotropies in body-wave velocities. We conclude with a section citing the 1983–1986 rock mechanics literature by category.

Rheology of the lithosphere: Selected topics

Attenuation of shear-waves in the lithosphere for frequencies from 0.05 to 25 Hz

Patterns in the spatial distribution of organisms provide important information about mechanisms that regulate the diversity of life and the complexity of ecosystems. Although microorganisms may comprise much of the Earth's biodiversity and have critical roles in biogeochemistry and ecosystem functioning, little is known about their spatial diversification. Here we present quantitative estimates of microbial community turnover at local and regional scales using the largest spatially explicit microbial diversity data set available (> 10(6) sample pairs). Turnover rates were small across large geographical distances, of similar magnitude when measured within distinct habitats, and did not increase going from one vegetation type to another. The taxa-area relationship of these terrestrial microbial eukaryotes was relatively flat (slope z = 0.074) and consistent with those reported in aquatic habitats. This suggests that despite high local diversity, microorganisms may have only moderate regional diversity. We show how turnover patterns can be used to project taxa-area relationships up to whole continents. Taxa dissimilarities across continents and between them would strengthen these projections. Such data do not yet exist, but would be feasible to collect.

Spatial scaling of microbial eukaryote diversity

Evolution of the western pacific and its margin

SUMMARY Earthquake prediction research has been conducted for over 100 years with no obvious successes. Claims of breakthroughs have failed to withstand scrutiny. Extensive searches have failed to find reliable precursors. Theoretical work suggests that faulting is a non-linear process which is highly sensitive to unmeasurably fine details of the state of the Earth in a large volume, not just in the immediate vicinity of the hypocentre. Any small earthquake thus has some probability of cascading into a large event. Reliable issuing of alarms of imminent large earthquakes appears to be effectively impossible. Key word: Earthquake prediction.

Earthquake prediction: a critical review

Precursory changes in the radon concentration of groundwater were observed prior to the Izu-Oshima-kinkai earthquake (magnitude 7.0) 14 January 1978. The distance from the epicenter to a continuous radon-monitoring station at Nakaizu was about 25 kilometers. A sudden drop and a subsequent increase in the radon concentration recorded on 9 January 1978 were significant. The size of the spike-like change was about 15 percent. After the earthquake, a remarkable increase in the radon concentration occurred.

Radon Anomaly: A Possible Precursor of the 1978 Izu-Oshima-kinkai Earthquake.

Observation of Earthquakes and Explosions at the Bottom of the Western Pacific: Structure of Oceanic Lithosphere Revealed by Longshot Experiment

If the value of Q, the specific dissipation coefficient of seismic waves, were constant over a wide range of frequencies, the attenuation of waves with shorter periods would be larger than the attenuation of waves with longer periods. Accordingly, the spectrum of P waves over the range of periods shorter than 1 sec. observed near foci when compared with their spectrum after travelling a certain distance in the mantle would provide a good method for determining the value of Q. As will be discussed later, attenuation in the crust is possibly greater than the attenuation in the mantle, and consequently it would be desirable to be able to observe P waves from distant deep earthquakes with a geophone buried under the Mohorovicic discontinuity. Such an investigation, free from complications introduced by the crust would give accurately the attenuation of P waves in the mantle. However, it is impossible to carry out such an idealized experiment and in order to study the attenuation in the mantle, we have to make a judicious choice of a recording site, such as one where the crust is less absorptive at high frequency P waves than is normally the case. If, in fact, the attenuation of the short period P waves is small in the mantle, the short period waves may be so attenuated in the crust or in the upper mantle, that the evidence of 'transparency' of the mantle for short period P waves may vanish, all because the observation is made at a station placed on a crust made of highly absorptive materials. The difference in the spectra of P waves recorded simultaneously at Tsukuba and at Matsushiro indicates the possibility of the above mentioned masking effect of a crust

Attenuation of Short Period P Waves in the Mantle

THE Central Basin Fault of the Philippine Sea is proposed as an extinct mid-oceanic ridge1,2 and seems to be a key to the development of the floor of the Philippine Sea. Though the fault seems to be aseismic on the basis of land networks, it is interesting to know whether microearthquakes occur in the vicinity of the fault. We put a sensitive ocean-bottom seismograph (OBS) in the median valley of the ridge (the width of which is only a few kilometres) and from its recordings have been able to deduce the existence of microearthquakes. It has also been possible to estimate P and S velocities for the top of the mantle and a Q structure for the upper mantle.

Toshi Asada

Papers

Radon Anomaly: A Possible Precursor of the 1978 Izu-Oshima-kinkai Earthquake.

Observation of Earthquakes and Explosions at the Bottom of the Western Pacific: Structure of Oceanic Lithosphere Revealed by Longshot Experiment

Attenuation of Short Period P Waves in the Mantle

Seismographic observation at the bottom of the Central Basin Fault of the Philippine Sea

Apparent velocity measurements on an oceanic lithosphere