Temporal change in groundwater level following the 1999 (Mw = 7.5) Chi-Chi earthquake, Taiwan

We examine the post‐seismic change in the groundwater level following the 1999 (M_w = 7.5) Chi‐Chi earthquake in central Taiwan, as recorded by a network of 70 evenly distributed hydrological stations over a large alluvial fan near the epicenter. Four types of post‐seismic responses may be distinguished. In type 1, the groundwater level declined exponentially with time following a coseismic rise. This was the most common response in the study area and occurred in unconsolidated sediments on the Choshui River fan. In type 2, the groundwater level rose exponentially with time following a coseismic fall. This occurred in the deformed and fractured sedimentary rocks in the foothills near the Chelungpu fault that ruptured in the Chi‐Chi earthquake. In type 3, the groundwater level continued to decline with time following a coseismic fall. This also occurred in the deformed and fractured sedimentary rocks near the ruptured fault. Finally, in type 4, the groundwater level, following a coseismic rise, stayed at the same level or even rose with time before it eventually declined. This occurred mostly in unconsolidated sediments along the coast of central Taiwan and along the Peikang Stream. We analyze these post‐seismic responses by using a one‐dimensional model. Together with the results from well test, the analysis show that the type 1 response may be explained by an aquifer model with coseismic recharge and post‐seismic subhorizontal discharge across a length of 500–5000 m; the type 2 response may be explained by a model of coseismic discharge and post‐seismic recharge from surface water; the type 3 response may be explained by a model of coseismic discharge and post‐seismic subhorizontal discharge across a length of 500–5000 m; and the type 4 response may be explained by a model of coseismic recharge and sustained post‐seismic recharge from surface water. The characteristic time for the post‐seismic changes is similar to that for the groundwater‐level decline during dry seasons before the earthquake, suggesting that there was no earthquake‐induced changes in the aquifer properties (i.e. hydraulic conductivity), confirming the earlier results from recession analyses of the post‐seismic streamflow elsewhere after several earthquakes.     

'United We Stand': American Attitudes toward (Muslim) Immigration Post-September 11th

Listen here, professor. You're the one that needs an American history lesson! You don't know nothing about Lady Liberty standing there in the harbor with her torch on high, saying 'Give me your poor, your dead-beats, your filthy.' -Archie Bunker All in the Family     

Networks and Neolithisation: sourcing obsidian from Körtik Tepe (SE Anatolia)

This paper details the use of obsidian sourcing to reconstruct networks of interaction (or ‘communities of practice’) amongst populations of south-eastern Anatolia and the Near East in the context of ‘Neolithisation’ during the late 11th–early 10th millennia BC. EDXRF was used to elementally characterise 120 artefacts of Epi-Palaeolithic – Pre-Pottery Neolithic A date from Körtik Tepe in south-eastern Anatolia. Four eastern Anatolian sources are represented, mainly Bingöl A/B and Nemrut Da?, plus the first evidence for the use of Mu? obsidian. When the source data is integrated with the artefacts' techno-typological attributes it is possible to locate the assemblage within an Upper Tigris tradition (with some interesting local differences), which stands in stark contrast to contemporary practices in northern Mesopotamia and the Levant. These local and regional distinctions support recent views of the Neolithic being much more heterogeneous, with a ‘mosaic’ of community-specific/local traditions of subsistence practices, raw material choices and lithic technologies during the Younger Dryas–Early Holocene.     

On the geochemistry of gases and noble gas isotopes (including 222Rn) in deep crustal fluids: the 4000 m KTB-pilot hole fluid production test 2002–03

The concentrations of H₂, O₂, CO₂, and concentrations and isotopic composition of the noble gases (including ²²²Rn), N₂, CH₄, and higher hydrocarbons dissolved in 4000 m deep‐seated fluids from a 12‐month fluid production test in the KTB pilot hole were analyzed. This determination of the gas geochemistry during the test in combination with the knowledge of the hydraulic data provides relevant information about the fluid hydraulics of the deep system. All gas concentrations and isotopic signatures, except for ²²²Rn, showed constancy during the course of the test. This, in combination with large fluid flow rates at a moderate water table drawdown, imply an almost infinite fluid reservoir in 4000 m depth. From the change in ²²²Rn‐activity as a function of pump rate, the contribution of smaller and wider pores to the overall fluid flow in an aquifer can be deduced. This ²²²Rn‐activity monitoring proved therefore to be a valuable instrument for the qualitative observation of the scavenging of pore and fracture surfaces, a hydraulic feature invisible to standard hydraulic testing tools. The observance of this scavenging effect is due to (i) the continuous on‐line geochemical monitoring, (ii) the durability of the test, (iii) a change in pump rate during the course of the test, and (iv) due to the short half‐life of ²²²Rn. The fluids have a 5.9% mantle He component, and a δ²¹Ne excess of 14%, and a noble gas model age of about (5.5–6.2) ± 2.0 Myr. The mean N₂/Ar‐ratio of 516 and δ¹⁵N‐data of about +1.5‰ indicates sedimentary or metamorphic origin of N₂. The hydrocarbons, amounting to 33 vol.% in the gas phase, are derived from thermal decomposition of marine organic matter of low maturity. But a key question, the identification of the potential source region of the fluids and the migration pathway, is still unidentified.     

Gas breakthrough pressure for hydrocarbon reservoir seal rocks: implications for the security of long-term CO2 storage in the Weyburn field

This paper reports a laboratory study of the gas breakthrough pressure for different gas/liquid systems in the Mississippian‐age Midale Evaporite. This low‐permeability rock formation is the seal rock for the Weyburn Field in southeastern Saskatchewan, Canada, where CO₂ is being injected into an oil reservoir for enhanced recovery and CO₂ storage. A technique for experimentally determining CO₂ breakthrough pressure at reservoir conditions is presented. Breakthrough pressures for N₂, CO₂ and CH₄ were measured with the selected seal‐rock samples. The maximum breakthrough pressure is over 30 MPa for N₂ and approximately 21 MPa for CO₂. The experimental results demonstrate that the Weyburn Midale Evaporite seal rock is of high sealing quality. Therefore, the Weyburn reservoir and Midale Beds can be used as a CO₂ storage site after abandonment. The measured results also show that the breakthrough pressure of a seal rock for a gas is nearly proportional to the interfacial tension of the gas/brine system. The breakthrough pressure of a CO₂/brine system is significantly reduced compared with that of a CH₄/brine system because of the much lower interfacial tension of the former. This implies that a seal rock that seals the original gas in a gas reservoir or an oil reservoir with a gas cap may not be tight enough to seal the injected CO₂ if the pressure during or after CO₂ injection is the same or higher than the original reservoir pressure. Therefore, reevaluation of the breakthrough pressure of seal rocks for a given reservoir is necessary and of highest priority once it is chosen as a CO₂ storage site.     

Impure and Worldly Geography:1 The Africanist Discourse of the Royal Geographical Society, 1831–73

The written networks through which knowledge is produced and circulated offer a focus for a theoretically informed critique of the formation of modern geographical knowledge. Drawing on deconstruction and colonial discourse theory, this paper presents a reading of the Royal Geographical Society's (RGS) published record of nineteenth-century African exploration. This discourse posits a racially unmarked subject-position as the condition of scientific discussion. The Society's geographical knowledge is shown to have been formed through the effacement of alternative subject-positions and the appropriation of other ways of knowing. It is suggested that closer attention to the discursive structures of written networks of knowledge might inform a more nuanced understanding of the reproduction of disciplined knowledge.     

Guaranteeing the Protection of Submerged Archaeological Sites Regardless of their Location: The UNESCO Convention on the Protection of the Underwater Cultural Heritage (2001)

The UNESCO 2001 Convention on the Protection of the Underwater Cultural Heritage represents a significant move forward in the global protection and management of underwater cultural heritage. This paper reviews the Convention’s most basic tenets, such as in situ preservation, refusing commercial recovery, encouraging the cooperation of States also beyond territorial waters, and the creation of international standards for underwater archaeology. It also discusses the Scientific and Technical Advisory Body and highlights the Convention’s current status as an important tool to preserve and protect an international maritime heritage.