مجله ژئوفیزیک ایران
سال هفدهم شماره 6 (پیاپی 63، Winter 2024)

In this work, we considered the role of the dynamic barrier weakening in winter in polar ozone depletion from late winter to spring with the example of the Arctic polar vortex dynamics in 2015/2016 and 2016/2017 by the vortex delineation method using geopotential. The main characteristics (vortex area, wind speed along the vortex edge, temperature and ozone mass mixing ratio inside the vortex) were calculated using the ERA5 reanalysis data based on the fact that the Arctic polar vortex edge at the 50, 70 and 100 hPa levels is determined by the geopotential values 19.5´104, 17.5´104 and 15.4´104 m2/s2, respectively. The geopotential values characterizing the polar vortex edge were determined from the maximum temperature gradient and maximum wind speed on average for 1979–2021. The dynamic barrier of the polar vortex contributes to lowering the temperature inside the vortex in the lower stratosphere and prevents the propagation of air masses into the vortex, creating conditions for ozone depletion from late winter to spring with the appearance of solar radiation. The polar vortex is characterized by the presence of a dynamic barrier, when the wind speed along the entire edge of the vortex is more than 20, 18 and 16 m/s at the 50, 70 and 100 hPa levels, respectively. In the winter-spring 2015/2016, almost no weakening of the dynamic barrier was observed, which contributed to a temperature decrease inside the vortex, the formation of polar stratospheric clouds and the subsequent occurrence of heterogeneous and photochemical reactions of ozone destruction, while in the winter 2016/2017, a frequent weakening of the dynamic barrier was observed in the lower stratosphere at the 50, 70 and 100 hPa levels, accompanied by an increase in temperature and ozone content inside the vortex as a result of the penetration of warm, ozone-rich air masses into the vortex.

Indonesia is a region that experiences frequent earthquakes, and therefore is highly prone to earthquake hazards. Elevated seismicity in Indonesia means that building models to understand and predict earthquake characteristics and their associated hazards is important. The goal of this research is to develop a supervised learning artificial neural network (ANN) application that can predict the magnitude of earthquake wave propagation (bar) and the direction of propagation of earthquake wave using some selected earthquake data (Mw 5-8) happened in Indonesia from 1996 to 2019. The data was taken from the United States Geological Survey (USGS) database and the Indonesian Agency for Meteorological, Climatological, and Geophysics (BMKG) database. The earthquake data used in the artificial neural network application consists of a hidden layer with four neurons and seven input neurons that contain earthquake parameters, including longitude, latitude, magnitude, depth, strike, dip, and rake, as well as one output neuron. The magnitude and direction of energy propagation of the earthquakes were successfully predicted using the ANN program. Excellent agreement between the results of ANN and those of Coulomb 3.3 software strongly indicates that the ANN program can be used as an alternative to the existing Coulomb 3.3 software. The ANN model can also be further applied to other earthquake data around the world. The results are expected to contribute to the development of earthquake detection software tools. With artificial intelligence, earthquake prediction software will be more effective and can reduce the risks of failure in predicting the magnitude and direction of earthquake wave propagation.

Simulation of near-surface weather parameters is a challenging process, especially in urban areas, because it is difficult to precisely identify surface characteristics in urban micro-scales. Different urban parameterizations for the representation of urban structure are coupled with numerical weather or climate models to improve the accuracy of the micro-scale simulations. In this study, the numerical results of the Weather Research and Forecasting model (WRF) with three different urban configurations, namely no urban canopy or the SLAB scheme, Single-Layer Urban Canopy Model (SLUCM) and Multi-Layer UCM or the Building Effect Parameterization (BEP) in the simulation of near-surface air temperature, relative humidity and wind speed are evaluated against the observations in Tehran Metropolis, during 15 to 29 June 2016. Overall, results show that SLUCM and BEP predict meteorological parameters more accurately than SLAB scheme. Although the performance of the model is not the same in different weather stations, comparing SLUCM and BEP results, on average, over four stations of Tehran shows that BEP results in minimum errors and the maximum Pearson coefficients. In addition, the more intense night-time urban heat island is also simulated in BEP (over 2.5°C) in comparison to SLUCM (1.5°C) and SLAB (0.5°C). However, the daytime UHI intensity is approximately simulated with the same intensity in the three mentioned simulations. Since high-resolution numerical simulations are time-consuming and expensive, current results can be used in other related studies to avoid extra costs.

Estimation of ground response during earthquake is gaining much attention in recent years. One of the most important parameters needed to achieve this goal is the shear wave velocity and its related parameters in the surface layers obtained by seismic geophysical tests in place or by laboratory measurements on intact soil samples. Field measurement of such parameter is accurate, but expensive as well as time consuming. Therefore, the need to estimate shear wave velocity using other soil parameters is justified. For example, the numbers of blows (N) from standard penetration test (SPT) are readily available for many sites where geotechnical investigations are carried out. This paper presents a development of reliable correlation between Vs measured by using other soil parameters such as density and shear modulus of soil and N measured using SPT at various sites in Chalus and Nowshahr regions in Mazandaran Province. For this purpose, the results of standard penetration tests conducted in 31 different sites in Chalus and Nowshahr areas were used. Correlation relations were obtained separately for all soils, cohesive and non-cohesive soils. The relationships obtained are within the range of those obtained worldwide for other sites and are comparable to them. Moreover, present correlations, having regression coefficients (R2) almost 0.92, indicated good prediction capability. The proposed relations obtained are useful for assessment of seismic microzoning of the region.

The Zagros fold-thrust belt of Iran, as a continental-continental collision zone, is one of the most seismically active regions of the world. In this research, statistical point pattern analysis of earthquake locations in this region during 1976-2019 and the assessment of spatial association between earthquakes and major active faults of the region were carried out. For this purpose, different measures, (e.g., Nearest Neighbor Ratio, Global Moran’s I and Local Getis-Ord’s Gi* indices) were estimated and computed for the data catalog. Additionally, the directional anisotropy of the earthquake epicenters distribution and earthquake-fault association were assessed. Results obtained indicate a completely clustered pattern of epicenters for the whole region and also indicate that earthquakes with greater magnitudes show higher degrees of clustering. Also, a spatial autocorrelation of higher values of magnitudes are observed. The spatial relationships of earthquake locations and active faults pattern indicates that the trend of maximum dispersion of epicenters for the whole region is remarkably parallel with the general trend of this belt, as well as with the dominant trend of the major active faults of the region. Moreover, toward the south of the region, an obvious change in the directional anisotropy of epicenters is observed. The results of this study indicate that spatial analysis techniques reliably could be employed for revealing the seismicity pattern in tectonically active regions.

Human beings have encountered numerous natural disasters over time, andthe phenomenon of earthquake is one of the most destructive of them.In recent years, the complex behavior of earthquakes in terms of time and space has been investigated using complex networks, which has enabled us to know the global characteristics of this phenomenon. Studies on the earthquakes using the network method are based on how the network is constructed. In this paper, by constructing the network, the spatio-temporal recurrence of earthquakes which occurred in the Zagros region and were recorded at all broadband and short-period stations of the Iranian Seismological Center (ISC, http://irsc.ut.ac.ir) are subject to statistical review. The results showed that in the Zagros area the spatial recurrenceis about 0.020 km, and the time recurrencefor all magnitudethresholds issimilar topower relationship ( ) witha = -0.9.

The north-south trending strike-slip faults within the basement of the Zagros fold and thrust belt, which are inherited from the Pan-African construction phase, were reactivated during the suturing and convergence of Arabia and Central Iran since the Late Cretaceous and influenced the NW-SE trending structures of the Zagros belt. Among most of these transverse faults, the Kazerun fault which delineates the western boundary of the salt plugs in the Zagros belt near longitude 51.5°E is described in detail as the most significant transverse strike-slip fault recognized in the belt. Here, during the course of our investigations we found new evidence indicating that the north-south trending Kazerun fault system can be extended southwards to the coast of the Persian Gulf as evidenced by a prominent escarpment marking the west side of the Mand anticline as well as the observations of surface faulting associated with the right-lateral motion of recent geomorphic features. However, the north-south trending Razak fault has also been recognized as one of the major transverse faults in the Zagros basement. Right-lateral strike-slip motion along the Razak fault strands can be inferred from the associated lateral offset of stream beds observed on satellite images, aerial photos and on the field. Unlike what have been previously suggested, this study concludes that the southern ends of some of the north-south trending strike-slip faults which cross the NW-SE structures of the Zagros belt are not turned into thrusts striking ESE, sub-parallel to the fold axes, but instead the southern continuation of the north-south trending faults can be extended southwards to the coast of the Persian Gulf and Saudi Arabia.