An earthquake catalogue for Turkey for the interval 1913–1970

An earthquake catalogue has been prepared for the whole area of Turkey (within latitudes 35.5° N to 42.5°N and longitudes 25.5°E to 45.0°E) for the years 1913 to 1970. By computer recalculation of all source parameters and by using a consistent system for magnitude determinations, we have aimed at the highest possible homogeneity and completeness within the limits given.     

Earthquake magnitude — recent research and current trends

The magnitude recommendations adopted by the IASPEI Assembly at Zürich in 1967 have had both a stabilizing and a stimulating effect on magnitude determinations and related research. From 1967 onwards, one magnitude research paper has appeared on the average almost every week, thus making this parameter the most studied one in seismology. New facilities and more accurate methods, e.g., concerning instrumental equipment and interpretation techniques, have made it possible to improve earlier achievements. The application of magnitude scales has been extended in all respects, e.g., with regard to epicentral distances, focal depths, wave types and wave periods. Magnitude—frequency relations have become the most investigated equations within seismology, observationally as well as theoretically. They have wide applications, e.g., for estimating the maximum magnitudes of future earthquakes — an important item in earthquake prediction. The magnitudes provide significant information on other source parameters, such as wave energy, fault length, seismic moment. Relations between different types of magnitude yield valuable information on source properties. For instance, relations between magnitudes based on body and surface waves are used for efficient discrimination between earthquakes and underground explosions. It is our purpose to review the magnitude development in the post-Zürich period (1967–1980), partly for geologists, tectonophysicists and engineers, who need an overview, partly for seismologists, who need an introduction to an overwhelmingly comprehensive literature.     

Fracture risk estimation for Swedish earthquakes

For Swedish earthquakes, the average magnitude increases gently with the focal depth, whereas the seismic wave energy exhibits significant maxima at 15, 23 and 28 km depth. The earthquake fracture risk is estimated to be about 10^?6 for an underground storage facility in a carefully selected site.     

Seismic energy mapping applied to Sweden

The release of seismic wave energy provides a dynamic seismicity parameter of general applicability. The moving-block method is used for the seismic energy mapping of Sweden. On this basis, some general problems connected with such mapping are discussed. Maps of this type may be useful for estimating other related quantities, e.g., the maximum magnitude to be expected at any point.     

Focal depth distribution of Swedish earthquakes

Instrumental and macroseismic focal depths of Swedish earthquakes show statistically a high degree of correlation. The majority of the earthquakes is located in the lower granite, probably associated with a low-velocity layer, whereas crustal discontinuities appear to be relatively less seismic.     

Short-period Rayleigh waves from near-surface events

Short-period fundamental-mode Rayleigh waves (Rg) are generally well recorded by short-period seismographs within about 600 km of seismic events, such as explosions, rockbursts and earthquakes, which occur in the upper 3 km of the crust. Studies of these waves from records at the Swedish seismograph network revealed their usefulness to elucidate both path and source properties. They exhibit normal dispersion which requires a superficial low-velocity layer of about 1 km thickness, in part probably weathered and fractured granite. This layer has considerably higher attenuation than underlying more competent rock. The existence of Rg in regional short-period records is a reliable indication of shallow focal depth, and, provided adequate calibration is available, quite accurate depth estimation would be possible from the amplitude ratio of Rg to Sg1.     

Use of C-Band frequencies for satellite navigation: benefits and drawbacks

Although not considered for the first generation of European Galileo satellites, the use of C-Band frequencies for navigation purposes may be taken into account for a future generation of Galileo. For this reason, a frequency band of 20 MHz bandwidth (5,010–5,030 MHz) has been allocated in the course of the World Radio Communications Conference 2000 held in Istanbul, Turkey. The use of C-Band navigation signals offers both advantages and drawbacks. One example is the ionospheric path delay which is inversely proportional to the (squared) carrier frequency and is therefore significantly smaller at C-Band. On the other hand, the use of C-Band frequencies results in increased attenuation effects such as free space loss or rainfall attenuation. It is therefore necessary to provide a detailed analysis of the effects of C-Band frequencies on the navigation process. In order to assess the feasibility of using C-Band frequencies, various aspects of signal propagation and satellite signal tracking at C-Band are examined in the context of this article. In particular, aspects like free space loss, atmospheric effects, foliage attenuation, code and carrier tracking performance, code noise, phase noise and multipath are discussed with respect to their performance at C-Band. In order to allow comparison with the current GPS system, the performance at C-Band is compared to the L-Band performance under similar or identical conditions. The results of this analysis will finally be discussed with respect to their impact on satellite payload and receiver design.

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Tracking Holocene environmental changes in an alpine lake sediment core: application of regional diatom calibration, geochemistry, and pollen

Diatom abundances in the surface sediment samples of 41 mountain lakes in the central Austrian Alps (Niedere Tauern) were related to environmental variables using multi-variate techniques. Canonical correspondence analysis (CCA) revealed that the pH, date of autumn mixing (A _mix), mean August water temperature (T _Aug), dissolved organic carbon (DOC), and relative water depth (Z _rel) made significant contributions to explain the diatom assemblage variation in the lakes of the training set. A weighted averaging partial least square regression and calibration model was used to establish Di-pH (R ² _boot= 0.72, RMSEP_boot= 0.131), and a thermistor measurements-based PLS model for A _mix (R ² _boot= 0.71, RMSEP_boot= 0.006 log₁₀ Julian days). The latter showed a better prediction than T _Aug, and was used in terms of climate change. These transfer functions, together with analyses of loss on ignition (LOI), the total carbon/nitrogen (C/N)-ratios, and selected pollen, were applied to an early to mid-Holocene (11.5–4 cal. ky BP) sediment core section from an Austrian Alpine treeline lake on crystalline bedrock. Additionally, passive sample scores in the CCA of the diatom training set were used to show trends in the variables DOC and Z _rel. During the early Holocene, diatoms indicative of increased pH, extended warm summers, and low water levels dominated. Between 10.2 and 7.6 cal. ky BP it was followed by diatom assemblages that indicated an increase in lake water depth and an earlier A _mix. The multi-proxy data suggest that the A _mix decline is the result of a series of snow-rich summer cool and wet climate fluctuations, which were divided by climate warming at ∼9 cal. ky BP. Increased A _mix, LOI and DOC, and the correspondent decline in the C/N-ratios, show subsequent climate warming between 7.3 and 6 cal. ky BP. The long-term trend in Di-pH indicates the impact of catchment-related processes during the early-Holocene, that were superimposed by climate.