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31.
John Dvorak Johannes Matahelumual Arnold T Okamura Harun Said Thomas J Casadevall Dedi Mulyadi 《Bulletin of Volcanology》1990,53(1):20-28
Tangkuban Parahu is an active stratovolcano located 17 km north of the city of Bandung in the province west Java, Indonesia. All historical eruptive activity at this volcano has been confined to a complex of explosive summit craters. About a dozen eruptions-mostly phreatic events- and 15 other periods of unrest, indicated by earthquakes or increased thermal activity, have been noted since 1829. The last magmatic eruption occurred in 1910. In late 1983, several small phreatic explosions originated from one of the summit craters. More recently, increased hydrothermal and earthquake activity occurred from late 1985 through 1986. Tilt measurements, using a spirit-level technique, have been made every few months since February 1981 in the summit region and along the south and east flanks of the volcano. Measurements made in the summit region indicated uplift since the start of these measurements through at least 1986. From 1981 to 1983, the average tilt rate at the edges of the summit craters was 40–50 microradians per year. After the 1983 phreatic activity, the tilt rate decreased by about a factor of five. Trilateration surveys across the summit craters and on the east flank of the volcano were conducted in 1983 and 1986. Most line length changes measured during this three-year period did not exceed the expected uncertainty of the technique (4 ppm). The lack of measurable horizontal strain across the summit craters seems to contradict the several years of tilt measurements. Using a point source of dilation in an elastic half-space to model tilt measurements, the pressure center at Tangkuban Parahu is located about 1.5 km beneath the southern part of the summit craters. This is beneath the epicentral area of an earthquake swarm that occurred in late 1983. The average rate in the volume of uplift from 1981 to 1983 was 3 million m3 per year; from 1983 to 1986 it averaged about 0.4 million m3 per year. Possible causes for this uplift are increased pressure within a very shallow magma body or heating and expansion of a confined aquifier. 相似文献
32.
In this research, experimental applications have been performed to reduce blast induced vibrations in open pit mines. For
this purpose, artificial discontinuity zones such as barrier holes and trench were opened in a dragline panel of Seyitomer
Lignite Enterprise, Kutahya, Turkey. Peak particle velocities in front of and behind them were measured by seismographs. In
this way, their effect against vibration was observed and compared. Barrier holes were opened 24 m deep through 3 parallel
lines and aligned at 1 m spacing. On the other hand, the trench had 8 m depth and 4 m width. During the research, 209 measurements
were taken belonging to 105 explosions. Twenty-eight explosions were carried out in the barrier holes experiments and 77 explosions
were carried out in the trench experiments. A decrease in vibration of 14.3–18.5% was obtained behind the barrier holes while
a decrease of 24.8–58.1% was provided by the trench. 相似文献
33.
John Dvorak Johannes Matahelumual Arnold T Okamura Harun Said Thomas J Casadevall Dedi Mulyadi 《Bulletin of Volcanology》1991,53(1):20-28
Tangkuban Parahu is an active stratovolcano located 17 km north of the city of Bandung in the province west Java, Indonesia. All historical eruptive activity at this volcano has been confined to a complex of explosive summit craters. About a dozen eruptions-mostly phreatic events- and 15 other periods of unrest, indicated by earthquakes or increased thermal activity, have been noted since 1829. The last magmatic eruption occurred in 1910. In late 1983, several small phreatic explosions originated from one of the summit craters. More recently, increased hydrothermal and earthquake activity occurred from late 1985 through 1986. Tilt measurements, using a spirit-level technique, have been made every few months since February 1981 in the summit region and along the south and east flanks of the volcano. Measurements made in the summit region indicated uplift since the start of these measurements through at least 1986. From 1981 to 1983, the average tilt rate at the edges of the summit craters was 40–50 microradians per year. After the 1983 phreatic activity, the tilt rate decreased by about a factor of five. Trilateration surveys across the summit craters and on the east flank of the volcano were conducted in 1983 and 1986. Most line length changes measured during this three-year period did not exceed the expected uncertainty of the technique (4 ppm). The lack of measurable horizontal strain across the summit craters seems to contradict the several years of tilt measurements. Using a point source of dilation in an elastic half-space to model tilt measurements, the pressure center at Tangkuban Parahu is located about 1.5 km beneath the southern part of the summit craters. This is beneath the epicentral area of an earthquake swarm that occurred in late 1983. The average rate in the volume of uplift from 1981 to 1983 was 3 million m3 per year; from 1983 to 1986 it averaged about 0.4 million m3 per year. Possible causes for this uplift are increased pressure within a very shallow magma body or heating and expansion of a confined aquifier. 相似文献
34.
Murat Ercanoglu Gülseren Dağdelenler Erman Özsayin Tolga Alkevlı Harun Sönmez N. Nur Özyurt Burcu Kahraman İbrahim Uçar Sinem Çetınkaya 《山地科学学报》2016,13(11):1923-1940
Landslide database construction is one of the most crucial stages of the landslide susceptibility mapping studies. Although there are many techniques for preparing landslide database in the literature, representative data selection from huge data sets is a challenging, and, to some extent, a subjective task. Thus, in order to produce reliable landslide susceptibility maps, data-driven, objective and representative database construction is a very important stage for these maps. This study mainly focuses on a landslide database construction task. In this study, it was aimed at building a representative landslide database extraction approach by using Chebyshev theorem to evaluate landslide susceptibility in a landslide prone area in the Western Black Sea region of Turkey. The study area was divided into two different parts such as training (Basin 1) and testing areas (Basin 2). A total of nine parameters such as topographical elevation, slope, aspect, planar and profile curvatures, stream power index, distance to drainage, normalized difference vegetation index and topographical wetness index were used in the study. Next, frequency distributions of the considered parameters in both landslide and nonlandslide areas were extracted using different sampling strategies, and a total of nine different landslide databases were obtained. Of these, eight databases were gathered by the methodology proposed by this study based on different standard deviations and algebraic multiplication of raster parameter maps. To evaluate landslide susceptibility, Artificial Neural Network method was used in the study area considering the different landslide and nonlandslide data. Finally, to assess the performances of the so-produced landslide susceptibility maps based on nine data sets, Area Under Curve (AUC) approach was implemented both in Basin 1 and Basin 2. The best performances (the greatest AUC values) were gathered by the landslide susceptibility map produced by two standard deviation database extracted by the Chebyshev theorem, as 0.873 and 0.761, respectively. Results revealed that the methodology proposed by this study is a powerful and objective approach in landslide susceptibility mapping. 相似文献
35.
Harun Rasid 《Natural Hazards》1993,8(1):39-57
Based on a systematic sample survey among the residents of two contrasting floodplain environments - the Tista floodplain (a shallow flood area) and the Ganges-Brahmaputra floodplain (a deep flood area) - this study tests a central hypothesis that the floodplain residents of Bangladesh preferred regulation of flood levels as the main flood alleviation measure. The study found that, despite significant differences in property setting, flood hazard experience and the nature of indigenous adjustments to floods between the two sample areas, an overwhelming 95% of the respondents from each area preferred regulation of flood levels within a range of 0.3 to 2.0 m. The study attempts to provide an explanation for the popularity of regulated flood levels in the context of indigenous adjustments of floodplain crops and infrastructures tonormal flood levels in Bangladesh, which coincided with the respondents' preferred range of flood levels. The study points out that the objective of the UNDP/World Bank-sponsored embankment compartmentalization projects also coincides with this goal of regulating flood levels. However, to test the physical limitations of regulating water levels between neighbouring compartments and to assess the environmental impacts of the proposed projects, the study stresses the need for initiating environmental baseline surveys on the pilot compartmentalization project, which is located on the left bank of the Brahmaputra. 相似文献
36.
Hiroaki Yamanaka Ögur Tuna Özmen Kosuke Chimoto Mehmet Akif Alkan Muammer Tün Emrah Pekkan Oguz Özel Derya Polat Murat Nurlu 《Journal of Seismology》2018,22(5):1127-1137
We have explored 1D S-wave velocity profiles of shallow and deep soil layers over a basement at strong motion stations in Eskisehir Province, Turkey. Microtremor array explorations were conducted at eight strong motion stations in the area to know shallow 1D S-wave velocity models. Rayleigh wave phase velocity at a frequency range from 3 to 30 Hz was estimated with the spatial autocorrelation analysis of array records of vertical microtremors at each station. Individual phase velocity was inverted to a shallow S-wave velocity profile. Low-velocity layers were identified at the stations in the basin. Site amplification factors from S-wave parts of earthquake records that had been estimated at the strong motion stations by Yamanaka et al. (2017) were inverted to the S-wave velocities and Q-values of the sedimentary layers. The depths to the basement with an S-wave velocity of 2.2 km/s are about 1 km in the central part of the basin, while the basement becomes shallow as 0.3 km in the marginal part of the basin. We finally discussed the effects of the shallow and deep sedimentary layers on the 1D S-wave amplification characteristics using the revealed profiles. It is found that the shallow soil layers have no significant effects in the amplification at a frequency range lower than 3 Hz in the area. 相似文献
37.
This study reported the mass mortality events (MMEs) of Pinna nobilis based on diving surveys in Turkey. Data were collected across 12 sites in the Aegean Sea, and one site in the Sea of Marmara, within the period of June-September 2019. The results showed that a low mortality rate of 10% was found in the Sea of Marmara, and a MME was not detected for this area. In contrast, 97% mortality was recorded for the P. nobilis population distributed in the Turkish Aegean Sea. This discrepancy might be related to the seawater temperature and salinity values of these two seas. The waters of the Sea of Marmara were colder and less salty than the Aegean Sea. The findings highlighted the importance of protecting the healthy population of critically endangered fan mussels in the Sea of Marmara. It was recommended that sound management plans comprising of monitoring, enforcement and public awareness activities could be implemented in order to achieve this. 相似文献
38.
Modelling palaeoglaciers in mountainous terrain is challenging due to the need for detailed ice flow computations in relatively narrow and steep valleys, high-resolution climate estimations, knowledge of pre-ice topography, and proxy-based palaeoclimate forcing. The Parallel Ice Sheet Model (PISM), a numerical model that approximates glacier sliding and deformation to simulate large ice sheets such as Greenland and Antarctica, was recently adapted to alpine environments. In an attempt to reconstruct the climate conditions during the Last Glacial Maximum (LGM) on Mount Dedegöl in SW Turkey, we used PISM and explored palaeoglacier dynamics at high spatial resolution (100 m) in a relatively small domain (225 km2). Palaeoice-flow fields were modelled as a function of present temperature and precipitation. Nine different palaeoclimate simulations were run to reach the steady-state glacier extents and the modelled glacial areas were compared with the field-based and chronologically well-established ice extents. Although our results provide a non-unique solution, best-fit scenarios indicate that the LGM climate on Mount Dedegöl was between 9.2 and 10.6 °C colder than today, while precipitation levels were the same as today. More humid (20% wetter) or arid (20% drier) conditions than today bring the palaeotemperature estimates to 7.7–8.8 or 11.5–13.2 °C lower than present, respectively. 相似文献
39.
Chin Yik Lin Mohd. Harun Abdullah Baba Musta Sarva Mangala Praveena Ahmad Zaharin Aris 《Natural Resources Research》2011,20(1):45-56
A total of 20 soil samples were collected from 10 boreholes constructed in the low lying area, which included ancillary samples
taken from the high elevation area. Redox processes were investigated in the soil as well as groundwater in the shallow groundwater
aquifer of Manukan Island, Sabah, Malaysia. Groundwater samples (n = 10) from each boreholes were also collected in the low lying area to understand the concentrations and behaviors of Fe
and Mn in the dissolved state. This study strives to obtain a general understanding of the stability behaviors on Fe and Mn
at the upper unsaturated and the lower-saturated soil horizons in the low lying area of Manukan Island as these elements usually
play a major role in the redox chemistry of the shallow groundwater. Thermodynamic calculations using PHREEQC showed that
the groundwater samples in the study area are oversaturated with respect to goethite, hematite, Fe(OH)3 and undersaturated with respect to manganite and pyrochroite. Low concentrations of Fe and Mn in the groundwater might be
probably due to the lack of minerals of iron and manganese oxides, which exist in the sandy aquifer. In fact, high organic
matters that present in the unsaturated horizon are believed to be responsible for the high Mn content in the soil. It was
observed that the soil samples collected from high elevation area (BK) comprises considerable amount of Fe in both unsaturated (6675.87 mg/kg) and saturated horizons (31440.49 mg/kg) compared
to the low Fe content in the low lying area. Based on the stability diagram, the groundwater composition lies within the stability
field for Mn2+ and Fe2+ under suboxic condition and very close to the FeS/Fe2+ stability boundary. This study also shows that both pH and Eh values comprise a strong negative value thus suggesting that
the redox potential is inversely dependent on the changes of pH. 相似文献
40.
We conducted archaeological and geophysical surveys in order to investigate the submergence of ancient constructions along the coast at Kekova Island in southern Turkey. Submerged archaeological remains were measured with respect to present sea level, and geological features that may have caused subsidence were determined by seismic investigation. We estimated relative sea‐level change taking into account presumed original elevation of constructions associated with the harbor at the time of occupation and compared our results with eustatic–isostatic sea‐level studies in the Mediterranean. Ceramics found along the submerged quay of Kekova Island provided evidence for the time of last use of the harbor structures and suggest that submergence began during the early Byzantine period. Considering relative sea‐level changes, eustatic–isostatic effects, and the period of submergence, we estimate a rate of coastal tectonic subsidence of at least 1.6 mm/yr over the last 1400 years. 相似文献