The authors are to be commended for their thorough and timely review [McDowell-Boyer et al., 1986] on the subject of particle transport through porous media. It was felt, however, that they have not followed far enough their own streams of thoughts. Despite the detailed descriptions of current perceptions how particles get separated from the carrying liquid and how they interact with the porous media, little attention was paid to the fact why they can be transported over hundreds of meters. The authors mentioned the studies by Smith et el.[1985], who reported microbial breakthrough at the 0.3-m depth of undisturbed soil columns within 17-50 min. Gerba and Goyal's [1985] study is also cited according to which bacteria had moved over distances of more than 800 m. However, no discussion is offered about the discrepancy between these and many other reported observations on fast and farreaching particle transport in porous media and the lack of models dealing with this kind of transport. Corapcioglu and Haridas [1985], for instance, presented an approach to the transport of microorganisms through porous media. No matter how these authors stressed the flow parameters (they went to the permissible limits), their model strongly indicated that bacteria cannot be transported over distances exceeding 0.2 m under the commonly accepted constrains of the model.The reasons for these deficiencies in the perception of particle transport through porous media, as they are well represented in this review article, can be traced back to the early beginnings of groundwater hydrology. It was Darcy's [1856] cracks. Voids which support particle transport have diameters at least an order of magnitude greater than the particles that move. This movement results in readily recognizable accumulations of silt (siltants) or clay (argilans) coatings on the surfaces of the voids, eventually plugging them. Filter theory conceptualizes the porous media as homogenous, whereas microscopists conceptualize the same media as inhomogeneous [Jeans, 1986; Bullock et al., 1985]. Thus surface accumulation is, indeed, observed but at much smaller scales. Pores only 50/•m wide are often distinctly lined with clay particles. Apparently, water carrying them through those pores lost its dragging power due to loss of momentum. This 10ss can be caused by decreasing flow velocity, by the reduction of mass flow due to water sorption into the finer pores surrounding the flow paths, or by any combination of the two. Gerba and Biton [1984], for instance, reported from groundwater flow studies that the bulk of larger Escherichia coil appeared about 1 hour earlier in an observation well 160 m downstream from an injection well than the bulk of the much smaller coliphage f2. Likewise, Harvey et al. [1986] reported that the peak abundance during fractional breakthrough of carboxylated microspheres at 1.5 m from the point of injection was highest for the 1.2-/•m diameter size class, followed by the 0.7-and 0.2-#m microspheres. This indicates that some of the larger partic...

The MW (moment magnitude) 7.9 Denali fault earthquake on 3 November 2002 was associated with 340 kilometers of surface rupture and was the largest strike-slip earthquake in North America in almost 150 years. It illuminates earthquake mechanics and hazards of large strike-slip faults. It began with thrusting on the previously unrecognized Susitna Glacier fault, continued with right-slip on the Denali fault, then took a right step and continued with right-slip on the Totschunda fault. There is good correlation between geologically observed and geophysically inferred moment release. The earthquake produced unusually strong distal effects in the rupture propagation direction, including triggered seismicity.