1.
Lukšić,
ABSTRACT:
The
paper analyzes homogeneous data of vapour pressure and relative humidity
recorded at the Zagreb-Grič observatory between 1944 and 1978.
The
mean annual course of vapour pressure resembles that of air temperature.
Relative humidity in the mean annual course decreases from January to April,
increases from April to June, slightly decreases from June to July, and then
increases until December; the major minimum in April is due to sudden heating
of air, and the major maximum in December is due to the prevalence nightly air
cooling. Singularities of vapour pressure (August 13-16) and of relative
humidity (January 21-27, May 4-9, June 8-15, December 21-27) have also been
determined.
The
mean diurnal course of vapour pressure has its major minimum early in the
morning, and its maximum is in the afternoon; from June until October
unpronounced secondary afternoon minimum appears. Relative humidity mean
diurnal course has its maximum about sunrise, and its minimum is in the
afternoon.
In
the 1944 – 1978 period, vapour pressure does not
show a pronounced trend, while relative humidity tends to increase in August
and September.
Numerous
atmospheric processes are reflected in the vapour pressure data and the
relative humidity data recorded on Grič. The processes are air advection, daily
heating and nightly cooling of air, evapotranspiration, condensation,
sublimation, vapour diffusion, vertical air mixing, subsidence, cyclonal
activity (precipitation, increased cloudiness), European monsoon, foehn
influence of the Dinaric mountains and the Alps, and, finally, the urban
influence. A combination of these processes often increases or decreases the
vapour pressure or relative humidity. The influence of these processes is generally
not constant throughout the year.
2.
Lisac,
ABSTRACT:
Presented
are the surface airflow characteristics in
3.
Penzar,
ABSTRACT:
The
paper deals with ground values of incoming Solar
energy in the 41° – 47°N zone and in the 0 – 3000 metre altitude
range, on the assumption of Rayleigh atmosphere model. The analysis is based on
daily global radiation. A comparison with measured data shows that daily
radiation for Rayleigh atmosphere model as a rule exceed that of real daily
radiation near the ground, especially at little altitudes. The radiation for a Rayleigh
model can be exceeded only rarely, in the case of relatively clear and dry air
and strong reflection on suitable situated clouds or on fresh snow. Rayleigh atmosphere
over
4.
Allegretti,
I., D. Skoko and M. Živčić (1984): Earthquake hypocentre determination by
analytical presentation of the Wadati’s graphical method (four
seismological stations). Geofizika,
1, 169-191. (in Croatian)
ABSTRACT:
In the series of papers about the shallow and deep earthquakes Japanese seismologist K. Wadati presented a graphical
method for the earthquake hypocentre determination. Due to its simplicity, it soon became well known as one of
the best methods for locating near earthquakes. In the first part of
this paper (Paragraphs 1., 2., 3.) all the details of
Wadati’s graphical method are presented. In Paragraph
4. original Wadati’s procedure is
presented in the analytical form. The solution of the
equations (Eqs. 1.-4) of the seismic waves
propagation is sought in the fixed rectangular coordinates. After the necessary
transformations the equations (15) are obtained. This equation is linear in
four unknowns: xo, yo,
and c2. To solve the system it is
necessary to form the equations for four seismological stations. The system
(16) combined with the equation (17) completely defines the position of the
hypocentre and the value of the constant c.
In Appendix A a method of coordinate transformations is presented according to
C. F. Richter (1958). It is somewhat simplified due to the linearity of
coefficients AC and B in the latitudes of
To complete the analysis of the data of an earthquakes, in Paragraph 5. the graphical and the analytical method of the hypocentral
time determination are presented. The graphical method is presented by the well
known Wadati’s diagram (Wadati, 1933) (Fig. 8 as example) while the
analytical method consists in the straight line fitting to the observational
data by the least squares method (Eq. 25., 28., -30.).
The describe method for the hypocentre
determination cannot be applied when all four seismological stations lie on the
straight line. This restriction is discussed in Appendix C where it is shown
that in the case of linearity between the station coordinates the corresponding
determination (3.C) is vanishing.
In Paragraph 6. an example is presented. The hypocentre of
the earthquake of 05. 02. 1969. at 04h 25m GMT
is determined applying both graphical (Fig. 3.) and the analytical procedure.
Some difficulties that may arise in the graphical procedure are also discussed,
in particular the case when the ration mik
(Eq. (5)) approaches unity.
It is shown that the analytical method
supersedes the graphical one in the precision of the results obtained,
convenience of the procedure and the speed of its application, especially when
an electronic computer is available.
5.
Živčić,
M.,
ABSTRACT:
The original
Wadati’s graphical method for the earthquake hypocentre location is
already presented in analytical form (Allegretti et al. 1984). However, the described method was restricted to the
use of the data of four seismological stations. In this paper the equations
(Eq. 1.) of seismic wave propagation are solved for the hypocentre coordinates x, y,
z and the constant c = Vp Vs/(Vp-Vs) by the use of the least
squares method. Providing that approximate values of x, y, z and c are known (usually it is sufficient to approximate the starting
epicentre coordinates x’, y’, with the coordinates of the
station with the minimal ts-tp time) the least squares
method is applied to the error equations (Eqs. 4.). Due to the high rate of
convergence it is sufficient to perform only a few iterations. This enables the
use of the greater number of seismological stations and, as a consequence, the
greater precision of the results. The error estimation is also possible giving
the quantitative measure of the precision of the results obtained. It is also,
shown, that Wadati’s method could be extended to include the seismic
station height differences. This may be applied in the rock bursts
investigations too.
6.
Herak,
D. and M. Herak (1984): Influence of parameters of an earth’s crust and
upper mantle model on Rayleigh waves dispersion. Geofizika, 1, 203-215. (in Croatian)
ABSTRACT:
In
this paper we considered the influences of the changes of the crust and upper
mantle earth model parameters on the Rayleigh waves
group velocity dispersion. Final result of such analysis is necessary as the
first step in the inversion of dissipation data for the earth interior.
The
partial derivatives of the group velocity with respect to the shear wave
velocity b
density r and
the layer thickness d were calculated
for the continental earth model PEM of Dziewonski et al. (1975), (Table 1). We
have modified the model by adding a thin sedimentary layer on top of it. The
Thompson-Haskel matrix method (see Appendix) was used for the calculation of
theoretical phase velocity dispersion curves with and without taking earth
sphericity into account (Fig. 1). Partial derivatives were calculated by the
finite difference method (equations (1), (2)). Figures 2, 3 and 4 represent the
partial derivatives curves with respect to b, r and
d, respectively. The numbers on the
curves denote the layers in which the parameter in question was changed.
The
conclusions of the analysis are the following:
(i)
Shear wave velocity shows the greatest influence upon
the group velocity of Rayleigh waves. The influence of the layer thickness is
more expressed, the thinner the layer is.
(ii)
Partial derivatives with respect to b
have peaks for periods that correspond to wave lengths of 3.45-3.80h (h
being the depth to the middle of the layer) except for the fourth layer where
the wave length equals 3.15h.
(iii)
Changing the layer thickness results mainly in
shifting the group velocity curves toward smaller or greater periods without
changing the value of the neighbouring extreme.
7.
Živčić,
M. (1984): Focal depth determination using macroseismic data. Geofizika, 1, 217-221. (in Croatian)
ABSTRACT:
The macroseismic
intensity – distance relation (Eq. 6) is defined through four parameters:
coefficient p, epicentral intensity Io, focal depth h and absorption coefficient. All the
known methods for parameter estimation were based on “a priori”
knowledge of the epicentral intensity and/or used a graphical procedure. Also,
the epicentral intensity was taken as discrete variable and the value to the
coefficient p was assigned in
advance. By considering the epicentral intensity as a continuous variable that
can achieve any value greater or equal to the maximum observed intensity, it
was possible in this paper to apply the least squares method for parameters
determination. The only assumption is that the starting values of the
parameters, that are to be determined, are roughly known. The procedure
consists in calculating the corrections to the starting values of parameters
until the best fit, in the sense of Eq. (17), is obtained. In this way the
focal depth determination does not depend on the assumptions contained in the assignment
of the epicentral intensity, and the imprecision of the graphical method is
avoided. The method could be applied for the determination of any combination
of the parameters of Eq. (6), providing that the number of observed isoseismal
radii is not less than the number of the parameters to be estimated. In the
cases where the number of observed isoseismal radii exceeds the number of the
parameters to be estimated, the error estimation is also possible, giving the
quantitative measure of the precision of the results obtained. Due to the
flexibility of the method and its applicability to the electronic computer the
parameter estimation is much faster and more precise than before.
8.
Živčić,
M. (1984): Extension of Geiger’s method for earthquake hypocentre
location. Geofizika, 1, 223-228. (in
Croatian)
ABSTRACT:
The method
of L. Geiger for earthquake hypocentre location, based on the knowledge of
seismic wave arrival times, is well discussed in seismological literature and
widely used. In this paper a simple extension of the method is suggested. It is
shown that the error equations could be formed from the arrival time differences
of the earthquake phases. In that way it has become possible to include, in the
determination of the hypocentre, the data from the stations with poor timing
system, as well as data from the strong motion records which usually operate
without the absolute time system. Also, due to the lack of accurate timing, it
was often impossible to locate instrumentally earthquakes from the beginning of
this century. The presented method is very convenient for relocation of those
events.