1.
Belinić, T. and S. Markušić: Empirical criteria for the accuracy of earthquake locations
on the Croatian territory.
This paper presents the empirically based ground truth criteria, or shorter
GT criteria, for the estimation of the epicentral location accuracy of the seismic
events recorded at network stations within 400 km around the city of Zagreb. The
criteria are based only on the network coverage metrics and the GT5 level represents
an absolute location error lower than 5 km. They have been developed using
a bootstrap resampling method: same earthquakes have been relocated many
times but with different, randomly selected seismic stations. We used 330 reference
events taken from the pages of ISC (ISC Reference Event Bulletin, 2008) and
showed that the location accuracy is most affected by the distance to the farthest
station in the seismic network, while not at all influenced by the distance to the
nearest. The developed GT criteria for GT595% level of accuracy require 10 or more
network stations, all within 125 km from the epicentre, and the secondary azimuthal
gap (the largest gap when any given station is removed from the network)
less than 200°, or the network quality metric (the deviation between the optimal
uniformly distributed network and the actual network) less than 0.41. The obtained
results revealed that the global criteria are too restrictive and unsuitable
for the studied area since they require more regular networks. With our criteria, it
is possible to achieve higher accuracy for the networks with a bigger secondary
azimuthal gap or greater network quality metric. In addition, our criteria limitations
are shown for the areas with simpler geological structure.
Keywords
: GT criteria, epicentral location accuracy, bootstrap method, Croatia [
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2.
Rodríguez, J. A. B., J. A. P. Fernández, A. R. Vega, F. de J. L. Saucedo and K. I. C. Carreón: Magnetic susceptibility
and natural gamma radioactivity as indirect proxies for characterization of sandstones and limestones of the Sabinas
basin.
An analysis of magnetic susceptibility and natural gamma radioactivity is
presented as indirect proxies of the characteristics of sandstones and limestones of
the Sabinas basin. These rocks are located in the sedimentary sequence ranging
from the Upper Jurassic to the Cretaceous. The magnetic susceptibility indicates
changes in the magnetic composition of these rocks and suggests changes in their
weathering degree. Ranges of values of magnetic susceptibility in sandstones and
limestones allow classifying them into different groups, suggesting variability regarding
conditions of origin and evolution. High values of magnetic susceptibility
in limestones can be linked to sedimentation in anoxic or reducing environment,
as well as with its siliciclastic content. The natural gamma radioactivity expressed
in the contents of Th and relationships U/K and Th/U also suggest the degree of
weathering of these rocks, mainly in the sandstones. These relations also highlight
others characteristics in the sandstones related the probable provenance of
sediments, its distance, degree of weathering and transport dynamics. Using the
values of U/K ratio in the sandstones, it is possible to suggest the probable
quartz-feldspar relationships. These ratio values classified rocks as arkose or
quartzarenite, indicating the maturity of the sandstones. According to the U/K
ratio values, most of these rocks which show little maturity are called arkose.
Using the values of the Th/U ratio, it is possible to suggest the textures of quartzarenites,
classifying them as rocks with fabric that is clast-supported or matrix-supported.
Keywords: magnetic susceptibility, natural gamma radioactivity, limestones,
sandstones, Sabinas basin [
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3.
Kowalczyk, K. and J. Rapiński: Robust network adjustment of vertical movements with GNSS data.
Long operation periods of GNSS stations give a possibility to use the data in
analyzing vertical crustal movements with the accuracy better than ?0.5 mm/y.
During the analysis, the reliability must be considered. This involves the choice of
the vertical crustal movements network adjustment method. In most cases, the
vertical crustal movements network models are designed as absolute and related
to the ellipsoid, where the movement is calculated on the basis of estimated station
coordinates. The other option is choosing differential relative models, where
GNSS vector coordinates are used. In this case, GNSS stations are connected and
vertical movements between them are calculated. In the next stage, the network
of vertical crustal movements is adjusted and the accuracy is assessed. The aim of
this article is to calculate and adjust the unadjusted trend based on GNSS time
series in an area located in Central Europe. The article presents the robust adjustment
method with a weighting scheme. The obtained results show that the accuracy
of vertical crustal movements model of 0.5 mm/y can be obtained from the
GNSS observations processing. Also the benefits coming from the application of
robust adjustment method are emphasized.
Keywords: vertical crustal movements in GNSS data, robust adjustment, weight in adjustment [
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4.
Rožić, N.: Quality evaluation of height movement kinematic model of the Earth's crust on the Croatian territory.
The paper presents the empirical use of height movement kinematic model of
Earth's crust created for territory of the Croatia, Slovenia and Bosnia and
Herzegovina, in order to determine the relative height displacements of crust discrete
points between different epochs. Also, presents the use of this model for the
purpose of direct levelling measurement reductions determination, from surveying
epoch to another unambiguously selected epoch, i.e. in purpose of height movement
effects elimination from levelling network node benchmarks. For Croatian
territory the quality of the kinematic model is indirectly tested, founded on the
comparison of levelling measurement accuracy criteria related to the state II order
levelling networks constituted with original and reduced levelling measurements.
Levelling lines of two levelling networks of the II order, on the area of two deliberately
selected and representative levelling loops of the Croatian state levelling
network of I order, were analyzed. An accuracy criterion, using the original measurements
and comparatively using the reduced measurements from their survey
epoch to the I order network surveying epoch, is determined. Comparative comparison
of the original and reduced measurement accuracy criteria is not clearly
and unequivocally confirmed, nor completely rejected, the adequacy of the kinematic
model quality for measurement reductions determination. However, comparison
points to the fact that the quality of the kinematic model enables reliable
determination of the relative height displacements at the centimeter level.
Keywords: kinematic model, height displacements, height movement, quality,
measurement reduction, Croatia [
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5.
Adetokunbo, P., O. A. Sanuade, P. Edigbue, K. Adegbola and T. Daramola: Statistical analysis of data processing
in some seismic refraction methods: A synthetic data example.
The delay time method has gained attention in shallow seismic refraction
survey because it has the capability to map the lateral thickness of overburden
and relief of bedrock. This study addresses the comparison between the performances
of the plus-minus and conventional reciprocal methods using a synthetic
data. The interpretations obtained from both methods are reasonably comparable
to the actual geophysical models. This suggests that either of the methods can be
used to construct a geologic section. However, the result of randomized complete
block design (RCBD) experiment shows a significant difference in the type of
method used and this necessitate the need for further test. The pairwise comparison
suggests that the plus-minus method produces a model that better mimics the
actual data than the conventional reciprocal method.
Keywords: seismic refraction, plus-minus method, conventional reciprocal
method, RCBD [
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6.
Vujić, E., M. Brkić and M. Pavasović: Recent geomagnetic investigations of Palagruža island.
Intention of this work was to examine all available recent geomagnetic survey
data, in order to assess Palagruža as a potential location for a permanent variometer
station. The most recent data consist of absolute, total intensity vertical
gradients and Overhauser effect dIdD vector measurements, carried out in period
2008-2010. Evidences were found in low crustal field estimates, relatively low total
field vertical gradient distribution over the island, quite high time series correlation
with the near observatories, as well as in low noise level of geomagnetic
components. These preliminary results indicate Palagruža as appropriate location
for the repeat station as well as for the variometer station. However, additional
investigations of the geomagnetic sea and coastal effects by using much longer
time series are needed.
Keywords: geomagnetic repeat station, geomagnetic variometer station, crustal
field, geomagnetic induction arrow [
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7.
Amiri-Bourkhani, M., M. R. Khaledian, A. Ashrafzadeh and A. Shahnazari: The temporal and spatial variations
in groundwater salinity in Mazandaran Plain, Iran, during a long-term period of 26 years.
Groundwater resources are one of the main sources of water supply for agricultural
sector in Iran. Therefore, this study aimed to investigate the situation of
groundwater salinity in Mazandaran for use in agriculture. In this study, statistical
analysis of collected data, proper semivariogram model selection, cross validation
of predictions and preparing probabilistic and zoning maps using geostatistical
tools in the ArcGIS software, were performed. To investigate the spatial
variations and preparing zoning maps of water salinity, ordinary kriging (OK)
was used and the zoning maps were prepared. Spatial structure of electrical conductivity
(EC) assessment showed a moderate spatial dependence in most years.
Zoning and probabilistic maps of EC showed that the salinity of groundwater will
be added and the most probable salinity is related the lowland areas in the eastern
part of the plain. The use of this groundwater for irrigation in the long term
can decrease the rice yield and faced rice production with a serious risk. The results
of the Mann-Kendall and the Sen tests indicated a decreasing trend in the
area of groundwater with EC higher than one dS/m in Mazandaran plain that this
expressing an improvement in the quality of groundwater in the plain.
Keywords: ArcGIS, geostatistics, rice, trend [
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8.
Ružičić, S., Z. Kovač, Z. Nakić and D. Kireta: Fluvisol permeability estimation using soil water content
variability.
The use of unsaturated hydraulic conductivity can help to define soil permeability,
i.e. can contribute to the estimation of water percolation through unsaturated
zone. The goal of this paper was the estimation of soil permeability at the
location of case study profile Kosnica,
situated in the alluvial plain of the Zagreb
aquifer, Croatia, based on the variation in soil water content. Zagreb aquifer represents
the only source of potable water for inhabitants of the City of Zagreb and
Zagreb County. The thickness of unsaturated zone of the Zagreb aquifer varies
from 8 meters in NW part to 2 meters in SE part. The unsaturated hydraulic conductivity
values were calculated according to the granulometric composition of soil
horizons and with optimized soil parameters. Variation in unsaturated hydraulic
conductivity showed that the upper part of the soil profile was generally permeable
throughout the 2011/2012 hydrologic year. The unsaturated hydraulic conductivity
calculated with optimized soil parameters gave the highest values, always
greater than 1E-9 m/s. Even though the estimation of soil profile
permeability would be more precise with measurements of water content and
pressure head in each soil horizon, calculation performed in this manner can give
the first insight in general estimation of the unsaturated hydraulic conductivity
variability and related soil permeability.
Keywords: soil permeability, unsaturated hydraulic conductivity, water
content, well field Kosnica [
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9.
Pavlić, K., Z. Kovač and T. Jurlina: Trend analysis of mean and high flows in response to climate warming
- Evidence from karstic catchments in Croatia.
Persistence and evolution of trends of mean and high river flows from six
hydrological stations on watercourses of the Kupa River (Kupari, Kamanje), tributary
Čabranka (Zamost 2), Dobra River (Stative donje, Trošmarija), Mrežnica
River (Mrzlo polje) and annual precipitation on three meteorological stations
(Parg, Ogulin and Karlovac) were analysed. The paper focuses on seven indicators:
annual mean flow, seasonal mean flows (winter and summer mean flows),
instantaneous annual maximum flow, annual and seasonal precipitation.
Analysed time series range from 1951 to 2013, and the fixed period ranges from
1984 to 2013. Time series of each indicator was scaled to standardized flow anomaly
and was analysed using the Mann-Kendall Z test for monotonic trend, after
which it is smoothed using LOESS algorithm. The analysis was conducted for
each indicator for full record, e.g. 1951-2013,
then 1952-2013 and so on until
1984-2013. Thus, the sample size varies from 63 to 30 years. The smoothed standardized
flow anomaly is easily comparable among different hydrologic stations.
The standardized flow anomaly on all analysed stations for all analysed indicators
shows lower mean value than long-time average after mid-1980's, when fixed period
starts. Further analysis of summer and winter seasonal mean flows revealed
different deviation from long-term annual flow average. Trend evolution of certain
indicators was proven using Mann-Kendall Z test, by plotting Z values for each
iteration of start year (1951 to 1984).
Keywords: Mann-Kendall, precipitation, river flows, trend evolution, trend
persistence [
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10.
Nimac, I. and I. Herceg-Bulić: An intermediate complexity AGCM simulations of climate response to
a doubling of atmospheric carbon dioxide.
Atmospheric response to doubled carbon dioxide concentration is estimated
by analyzing 35-member ensemble mean made by an atmospheric general circulation
model of intermediate complexity. Simulated changes in the mean fields are
evaluated for winter (January-February-March) and summer (July-August-
September) seasons. Results show that doubled CO2 concentration causes warming
of around 2 °C at all levels in the model. At the surface, the largest temperature
change is found over the polar areas; while at the higher levels considerable
warming is found mostly over the continental parts. Atmospheric warming at the
300 hPa level is accompanied by cooling over the polar areas. At the levels above
300 hPa, temperature drops globally. Changes in jet stream occur at Northern
Hemisphere with larger winter amplitudes. During the respective winter, stratiform
precipitation significantly increases at the higher latitudes of both hemispheres
and decreases mostly over the oceans. Over the Northern Hemisphere,
convective precipitation is significantly increased during the summer. Over the
southern part of tropical Pacific, stratiform and convective precipitation is decreased
during the both seasons. Results also demonstrate that indirect impact of
increased CO2 concentration (i.e. effects associated
with changes in the lower boundary conditions) generally has a stronger contribution to the
tropospheric warming than direct CO2 impact (i.e.
the impact associated with absorption and emission of longwave radiation).
Keywords: climate change, doubled carbon dioxide concentration, intermediate
complexity model, direct CO2 effect, indirect CO2 effect [
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11.
Yasuda, H., B. Nandintsetseg, R. Berndtsson, G. Amgalan, M. Shinoda and T. Kawai: The effects of ocean SST dipole
on Mongolian summer rainfall.
Cross-correlations between inter-annual summer rainfall time series (June
to August: JJA) for arid Mongolia and global sea surface temperatures (GSST)
were calculated for prediction purposes. Prediction of summer rainfall for four
vegetation zones, Desert Steppe (DS), Steppe (ST), Forest Steppe (FS), and High
Mountain (HM) using GSSTs for time lags of 5, 6, and 7 months prior to JJA rainfall
was evaluated. Mongolian summer rainfall is correlated with global SSTs. In
particular, the summer rainfall of FS and HM displayed high and statistically significant
correlations with SST in specific parts of the oceans. SST dipoles (pairs of
positively and negatively correlated areas) were identified, and correlation for
time series of the SST differences between SST dipoles (positive - negative) with
the summer rainfall time series was larger than the original correlations. To predict
the summer rainfall from SST, an artificial neural network (ANN) model was
used. Time series of the SST difference that represents the strength of the dipole
were used as input to the ANN model, and Mongolian summer rainfall was predicted
5, 6, and 7 months ahead in time. The predicted summer rainfall compared
reasonably well with the observed rainfall in the four different vegetation zones.
This implies that the model can be used to predict summer rainfall for the four
main Mongolian vegetation zones with good accuracy.
Keywords: artificial neural network, dryland, Mongolian rainfall,
rainfall prediction, SST teleconnection [
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