Seismic moment tensors and kinematic source parameters

Summary. Parameters pertaining to the kinematics of a finite source are usually estimated by fitting specific fault models to the data. On the other hand, these parameters, including source location, are also contained in the moment tensors of higher degree. In this paper, the seismic response is represented in terms of 20 source parameters which are related to components of the moment tensors; they are also related to the parameters of fault models, as will be demonstrated for a number of 'classical' models. A linearized inversion for the moment tensor shows that with real data, or with realistic synthetic data, the results are not necessarily physically meaningful, unless constraints are imposed. The constraints are precisely those appearing as a priori assumptions in the conventional methods of source analysis; it is thus possible to investigate the impact of these assumptions. We will discuss in particular the assumption of a general deviatoric point source (not necessarily a double couple) versus that of a plane fault in finite sources. Although at this stage experience with practical performance of the new method is limited, it is suggested that in the appropriate circumstances constrained inversion for the seismic moment tensors offers a viable alternative to estimate kinematic source parameters.     

Faulting associated with historical and recent earthquakes in the Eastern Mediterranean region

This paper summarizes evidence for surface faulting in historical and recent earthquakes in the Eastern Mediterranean region and in the Middle East. Such information is particularly important for studies of active tectonics and for palaeoseismology. We have found 78 cases of faulting pre-1900 and 72 post-1900, some of which show that faults that have apparently been inactive this century had already ruptured before 1900. For some cases faulting could not have been predicted from 20th century activity, and in others it could have been expected, but has not been observed during the instrumental period. The data are sufficient to allow the derivation of relationships between magnitude and rupture length.     

Reappraisal of surface wave magnitudes in the Eastern Mediterranean region and the Middle East

We report on a detailed palaeomagnetic study of the Miocene Farellones volcanic formation in the Chilean Andes near Santiago (two sections, 37 sites, about 400 orientated cores). Petrological observations show evidence of low-grade metamorphism increasing downwards through the volcanic sequence. Optical observations of opaque minerals and magnetic experiments suggest that in many cases maghemitization is associated with hydrothermal alteration. However, thermal demagnetization data indicate that the low-grade metamorphism did not significantly modify the direction of the primary remanent magnetization recorded at the time of emplacement of the volcanic lava flows. Four intervals of polarity with two intermediate palaeodirections were observed in the ~650-m-thick composite section. According to the dispersion of flow average directions, palaeosecular variation was slightly larger than that observed in general during the Upper Cenozoic. The site mean directions obtained in this study differ significantly from the expected Miocene direction. Clockwise rotations of up to 20° of small blocks are probably associated with the deformation of the Andean Cordillera since middle Miocene times. Geomagnetic palaeointensity data were obtained, using the Thellier method, on 24 samples from eight distinct lava flows. The flow mean VDM varies from 1.4 to 4.0 × 10²² A m⁻². Altogether, our data seem to suggest the existence of a relatively low geomagnetic field undergoing large fluctuations. Although a linear relationship was observed between the natural remanent magnetization and the thermal remanent magnetization acquired during the Thellier–Thellier experiments, undetected chemical alteration of the magnetic minerals during hydrothermalism may also explain the unusually low palaeointensity obtained.     

Smaller source earthquakes and improved measuring techniques allow the largest earthquakes in Iceland to be stress forecast (with hindsight)

A group of three earthquakes in 2000 June in SW Iceland included the two largest earthquakes in Iceland in the past 30 yr. Previously, temporal changes in shear-wave splitting had not been recognized before these earthquakes as there were too few small earthquakes to provide adequate shear-wave data, and they were not stress forecast, even with hindsight. These large earthquakes were subject to a special investigation by the European Community funded PREPARED Project during which the seismic catalogue was extended to include smaller magnitude earthquakes. This more detailed data set, together with a semi-automatic programme for measuring the parameters of shear-wave splitting greatly increased the number of time-delay measurements.
The new measurements displayed the typical temporal variations before larger earthquakes as seen elsewhere: a long-term increase in time delays, interpreted as stress accumulation before the earthquake; and a decrease, interpreted as crack coalescence, immediately prior to the earthquake. The logarithms of the durations of both the implied accumulation of stress and the crack coalescence have the same self-similar relationships to earthquake magnitude as found elsewhere in Iceland. This means that, in principle, the time and magnitude of the larger earthquakes could have been stress forecast in real time had the smaller source earthquakes of the extended catalogue and the improved measuring procedures been available at the time.     

Water resource conflicts in the Middle East

This article discusses the causes and sources of water resource conflict in the 3 major international river basins of the Middle East: the Tigris-Euphrates, the Nile, and the Jordan-Yarmuk. The physical geography of the Middle East is arid due to descending air, northeast trade winds, the southerly location, and high evaporation rates. Only Turkey, Iran, and Lebanon have adequate rainfall for population needs. Their mountainous geography and more northerly locations intercept rain and snow bearing westerly winds in winter. Parts of every other country are vulnerable to water shortages. Rainfall is irregular. Water resource conflicts are due to growing populations, economic development, rising standards of living, technological developments, political fragmentation, and poor water management. Immigration to the Jordan-Yarmuk watershed has added to population growth in this location. Over 50% of the population in the Middle East lives in urban areas where populations consume 10-12 times more water than those in rural areas. Water is wasted in irrigation schemes and huge dams with reservoirs where increased evaporation occurs. Technology results in greater water extraction of shallow groundwater and pollution of rivers and aquifers. British colonial government control led to reduced friction in most of the Nile basin. Now all ethnic groups have become more competitive and nationalistic. The Cold War restrained some of the conflict. Israel obtains 40% of its water from aquifers beneath the West Bank and Gaza. Geopolitical factors determine the mutual goodwill in managing international water. The 3 major water basins in the Middle East pose the greatest risk of water disputes. Possible solutions include conservation, better management, prioritizing uses, technological solutions, increased cooperation among co-riparians, developing better and enforceable international water laws, and reducing population growth rates.     

Water in the Middle East peace process

Water resources occupy an important role in the bilateral negotiations of the Middle East peace process. This paper mentions the conflicting water plans for the utilization of the Jordan basin by Arabs and Israelis, and describes the issues that are to be handled in the process of peacemaking. It defines the water issues between Israel and each of its neighbouring entities: Jordan, the Palestinians, Syria and Lebanon, and reviews what has been addressed in the peace negotiations thus far. A more detailed review is made of the negotiation tracks where progress was made, and a less detailed review is made of the negotiations that settled the water dispute between Jordan and Israel. The paper alludes to the claims of water wars in the region and provides evidence that water has not been a catalyst for war in the Middle East. It also proposes some topics for research that can be of interest to alleviate water shortage.