None of the standard porosity-velocity models (e.g. the time-average equation, Raymer's equations) is satisfactory for interpreting well-logging data over a broad depth range. Clays in the section are the usual source of the difficulty through the bias and scatter that they introduce into the relationship between porosity and P-wave transit time. Because clays are composed of fine sheet-like particles, they normally form pores with much smaller aspect ratios than those associated with sand grains. This difference in pore geometry provides the key to obtaining more consistent resistivity and sonic log interpretations.A velocity model for Clay-sand mixtures has been developed in terms of the Kuster and Toksöz, effective medium and Gassmann theories. In this model, the total pore space is assumed to consist of two parts: (1) pores associated with sand grains and (2) pores associated with clays (including bound water). The essential feature of the model is the assumption that the geometry of pores associated with sand grains is significantly different from that associated with clays. Because of this, porosity in shales affects elastic compliance differently from porosity in sandStones. The predictive power of the model is demonstrated by the agreement between its predictions and laboratory measurements and by its ability to predict sonic logs from other logs over large depth intervals where formations vary from unconsolidated to consolidated sandstones and shales.

Most crustal rocks are anisotropic. Anisotropy may result due to depositional pore fabric development, diagenesis, and preferred directions of microcracks and crystallographic alignments. To further the understanding between some of these mechanisms and commonly measured rock physics properties (ultrasonic velocity, permeability and porosity), we developed a novel apparatus capable of measuring these parameters simultaneously at hydrostatic pressures up to 100MPa. First, we determine the average 3-D void space shape and orientation using the methods of Anisotropy of Magnetic Susceptibility and acoustic wave velocity (P-wave and Swave) to identify the principal anisotropy axes under ambient laboratory conditions. This directional anisotropy data is then used to guide experiments under hydrostatic pressure, where permeability, porosity and ultrasonic velocity are measured simultaneously from 5 to 90 MPa. We describe the use of these methods in an comparative study using two sandstones (Bentheim and Crab Orchard) to investigate the relationship between permeability, acoustic anisotropy, and pore fabric geometry.We find the structural anisotropy formed by the void space is well described by velocity anisotropy in both cases. At ambient (room) pressure, Crab Orchard sandstone has a velocity anisotropy of 19.1% and 7.6% (for P-waves and S-waves respectively). In contrast Bentheim sandstone possesses a weaker anisotropy of 4.7% and 3.0% for P-wave and S-wave velocity respectively. Under hydrostatic pressure, the acoustic anisotropy of Crab Orchard sandstone decreases rapidly from 3% and 7% at 5MPa (P-wave and S-wave) to 1.5% and 1% respectively at effective pressures over 40MPa; while for Bentheim sandstone the decrease is considerably less.Permeability of Crab Orchard sandstone is 125x10 -18 m 2 , decreasing rapidly as effective pressure increases. Fluid flow is highly dependent on direction with respect to pore fabric; permeability parallel to bedding is approximately twice that normal to bedding. In contrast, permeability of Bentheim sandstone is 0.86x10 -12 m 2 , and varies little with effective pressure or coring direction. We relate many of our measurements made under hydrostatic pressure to the contrasting pore fabric between the two rock types, and infer that a critical pressure is required for the initiation of crack closure, as expected from many models cited in the literature.

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Although religion often comprises a central component of the social and cultural make-up of communities in developing countries affected by disasters, there is often limited understanding of how religious faith, religious leaders, and religious institutions contribute to vulnerability and resilience in the post-disaster period. Using a case study related to the earthquake in Yogyakarta, Indonesia, in 2006, our research examined the role of faith and religion from the perspective of affected populations, including individuals, religious leaders, and academics. The research suggests complexity in fatalistic thinking and the role of religious activities, where both vulnerability and resilience co-existed. The nature of religious leadership was found to be highly dependent on the individual, although leaders primarily saw their roles as supporting the psychological recovery of the affected population. Examining religious institutions suggests that physical structures, collective engagement in activities, networks, and theological perspectives provided opportunities for initiatives aiming at disaster risk reduction, although not all of these aspects remain functional in the aftermath of disasters. The article concludes by discussing the importance of incorporating religious faith and institutions in disaster risk reduction programming and unifying messages between faith and non-faith organizations.