دکتر سعید زارعی

Floods have been considered the most common natural disaster worldwide in recent years. Flood hazard potential mapping is required for the management and mitigation of flood. Climatic change and the occupation of rivers and drainage have led to floods in arid areas. The objective of this study is to assess and zoning flood risk using the AHP-FUZZY hybrid approach model in the Dashti region of Bushehr Province.  In this study, precipitation, elevation, slope, drainage density, land use, geology and soil parameters were used. These parameters have been constructed and classified in the ARC GIS Software; which were weighed according to the AHP method in AHP SOLVER software and the layers were fuzzy using the fuzzy model. Finally, by combining the AHP-FUZZY method, the flood risk assessment and zoning map were obtained.6.5% of the area is in the very high-risk range, and 27.9% is in the high-risk range.  Analysis of the final map shows that Khormuj, Sana and Shonbeh are at greater risk of flooding. The combination of the AHP-FUZZY method in previous research has confirmed that this method has great capacity in flood risk assessment and zoning. Therefore, knowing the flood potential of the basin can be effective in formulating crisis management plans when faced with floods.

During the last two decades, the south part of seismotectonic zone of Zagros (Fars) was active. The Zagros seismotectonic belt consists of a series of fault-related folds that within their evolution, seismic areas and hydrocarbon reservoirs formed. Although the characteristics of Zagros are well known, the distribution of active deformations, style of fault-related folds, and its seismotectonic behavior are among the features that require further investigation.    In this study, changes in seismic rate based on changes in seismic parameter (b-value) and fractal dimension of seismicity (D-value) have been investigated using instrumental seismic data in the period of 2000 to 2021. Total amount of b-value and D-value were calculated by the least square’s method and the correlation integral method, respectively. The map of these parameters was plotted by interpolation method.    Frequency-magnitude distribution power law (logN=a–bM) relates the cumulative number of earthquakes (N) to their magnitude (M). This ratio is frequently used in seismic studies. In this relationship, a-value describes the productivity and b-value characterizes relative size distribution of earthquakes. Most b-value studies associate the seismicity parameter with the physical properties of a particular zone.    Since the introduction of fractal in 1976, the fractal concept has covered a wide range of pure mathematics and many experimental aspects of engineering. It has found a comprehensive concept. We analyzed seismicity using the IIEES and IRSC catalog. Decreasing the b-value in the northeastern of study area indicates that stress is increasing, which may signal a future sizable earthquake. The spatial variation of b-value suggests that the SW segment is less stressed compared to the NE segment.Considering that the correlation coefficient is about -0.78, the probability of occurrence of large earthquakes on large area faults increases. The zoning map parameter b-value to D-value ratio found valuable information on the invariance property of the seismic variation scale in the area. These results suggest that this approach can be used as a useful tool to evaluate seismic power distribution on active seismotectonic regions.    According to the zoning maps and the identification of high stress zone in the study area, the north parts of MFF, around Jam and Farashband and in the later stages, Khormuj will be the main candidate areas for future earthquakes. The seismicity pattern analyzed does hold the key to understand the seismotectonics of the region.

Geometric analysis of fractures in calcareous reservoirs containing hydrocarbon resources is of particular importance. Knowing the location and distribution of fractures in such reservoirs can play an effective role in providing field development plans, determining suitable sites for new drilling and reducing exploration costs. This study was carried out to evaluate the relative frequency of fractures method to identify regional fractures in the Bibihakimeh oilfield. The required data have been extracted by analyzing the underground countor maps in the Bibihakimeh oilfield. Then, the accuracy of the fracture map prepared based on this method was evaluated with the relevant data of reservoir parameters in the studied oilfields. Data on mud loss, thermal gradient, overburden thickness, total organic carbon and production index confirm results obtained from the relative frequency of fractures in the center of the oilfield. Comparison of the results with the map of basement faults in the study area shows that the performance of these regional fractures has caused curvature development and fractures concentration in some parts of the Bibihakimeh oilfield. These regional fractures act as a conduit for heat transfer from the depth to the surface, which in turn has led to a sharp increase in thermal gradient and production in wells in the central parts of the studied oilfield.

The earthquake phenomenon has been explained by power-law relations with respect to magnitude, time andspace. Fractal is one such power-law relation, which is a two-point spatial correlation function for earthquakeepicenters [1-2]. It reflects the heterogeneity of seismic activity in a fault system. Another power-law relation is bvalue,which is a frequency-magnitude relation defined by Gutenberg-Richter [3]. The b-value of a region reflectsthe frequency-magnitude characteristics of seismogenic structures, stress distribution in space and depth [4-8].In this paper, the fractal dimension (D) obtained by the box-counting method as the most general approach forcalculating D (Turcott, 1989). According to this method, the study area was initially superimposed on a square gridsize 1 r . The unit square (r) of the area was divided into small squares of linear size 1 1 r / 2, r / 4 and 1 r / 8,sequentially. The geometry of fractals is calculated by power-law distribution and the potential D, is represented bythe fractal dimension:Ni=〖C⁄r〗_i^Dwhere, Ni is the number of objects, characterized by the linear dimension r, C; proportionality constant and Df fractal dimension, which is calculated by (Turcotte, 1992):D=(⁡Log((Ni+1)/Ni))/(Log(ri/(ri+1)))At simplest form of Equation (2), the fractal dimension was determined from the slope of the log N (ri)versus log (1/ri) plot.Log(N)=C+K log⁡(1/S)In this paper, b-value, spatial fractal dimension of seismicity and faults D (s and f) are used toevaluate the seismicity of the Khuzestan zone in Southwestern part of Zagros zone in time interval 1900 to 2018.The seismicity data of the Zagros zone are extracted from unified seismic catalog of the Iranian Plateau. Spatialvariations of b-value, D(s) and D(f) demonstrate large variations in seismicity behavior along the study area.
The most vulnerable regions for the occurrence of the large earthquakes in the study area considering thecomputed lowest b-values and the highest D-values. The relationships among DC -b are used to classify the level ofearthquake hazards for individual seismic source zones, in which the calibration curves illustrate a negativecorrelation among the DC and b values. It is observed that the relationship among b and D may be used forevaluation of seismicity and earthquake hazard assessment because of the high value for correlation coefficients andlimited scattering of the calculated parameters.The results indicate low b-values and high moderate D(s) and D(f) in the North study area while the Central and southwest is accompanied by low b-values and high D(s) in time interval 1900-2018, which indicates different stress release regimes in northeast and southwest parts of the study area. The Index Regime Stress )R'( in study area is 2.24±0.44, that shows convergent in southwest of Zagros.Fractal analyses of the active faults and earthquake show increasing values from southwest to northeast. Kriging zoning maps of fractal variations show this content. Fractal dimensions of faults and earthquake in the Khuzestan area show different values, which varied in the NE-SW direction. Based on these variations, the northwestern parts of the study area have more tectonic activity than the southeastern parts.The lack of faults outcrop in Zagros range, nonequality in faults mechanism, lack of conformity in distribution of earthquake epicenters by faults exist. Consume of many states rate of energy duration of folding process and difference in tectonic and structural style of Sundries part of the study area causes difference in the amount of fractal dimension in southeast Zagros.According to the zoning maps and the identification of high stress zone in the study area, the cities of Izeh, Baghmalek, Haftkel and in the later stages Masjed Soleiman and Ramhormoz along with the surrounding settlements will be introduced as the main candidate areas for future earthquakes.

The Zagros orogeny as a central part of the Alpine-Himalayan orogenic belt is one of the most seismically active intracontinental fold-and-thrust belts on the Earth, and has an important role in active tectonics of the Middle East. The Hormuz Salt and several intermediate decollement levels, appears to be responsible for the most aseismic deformation of the Zagros sedimentary cover, and also to control the development of a large panel of fold structures, from detachment to fault-propagation folds with varying wavelength and rooting depth. The Dalan anticline located in the Fars province and mantled by soft Oligo-Miocene sediments in SW of the Central Zagros. For the kinematic and geometric analysis of the anticline based on satellite images, geological maps and field observations, three structural cross section perpendicular to fold axis have been studied. Comparing the position of the Dalan fold axis and axial plane in the aa', bb' and cc' cross sections indicates that in the axis of the anticline was rotated about 15 degrees toward the southeast. Regard to interlimb angle estimations and Ramsay classifications from all three cross sections, Dalan anticline is the open fold and 1B-1C classes, respectively. Based on geometrical and kinematic analysis and comparison from studied models such as Sattarzadeh et al, (2000) and Mitra (2003), the Dalan anticline is detachment fold type and compatible with the Lift –off Model With syncline evacuation model. In this model, limb rotation, migration of ductile sediment in outer hinges and syncline to core of anticline occurred.

In this study, an improved picture of the ongoing crustal deformation field for the Zagros as an evolving foreland fold and thrust belt is presented by using an extensive combination of geodetic and seismic analysis. The significant amount of oblique Arabia–Eurasia convergence is currently absorbed within the Zagros. Part of the total available energy is used in seismic deformations and part of it is stored in faults as potential energy. The remaining energy is consumed by the creeps and aseismic processes. Estimation of moment rate is comparatively reckoned as a new method for investigation of tectonic activities rate in different regions. In this research, geodetic moment rate (based on the GPS data) and seismic moment rate (based on the historical and instrumental earthquake data) are estimated for Zagros block in S-SW of Iran. Each approach has its own limitations. In all parts of the Zagros belt, the maximum estimated moment rate belongs to geodetic moment rate which is almost equal to 7.441×1019 Nm/yr. The seismic moment rate in Zagros belt is almost equal to 3.438×1018 Nm/yr. In this study, different parts of the Zagros Mountain range are investigated using three methods (structural, tectonosedimentary and 1°×1° grid) and the results are compared and analyzed. The seismic moment rate of simply-folded belt, high Zagros and Khuzestan plain are 1.56 × 1018 Nm/yr, 1.45 × 1018 Nm/yr and 6.24 × 1016 Nm/yr, respectively. It means that the maximum (minimum) released energy belongs to simply-folded belt (Khuzestan plain). In Izeh, Central Lorestan, interior Fars and Bandar Abbas hinterland sub-zones, the maximum amount of energy has been released during the earthquakes. The ratio of the seismic moment rate to geodetic moment rate is near 0 (0.0429) which indicates that the aseismic processes dominate the deformation, or stress accumulation is underway which can increase the level of the seismic hazard. Such aseismic deformation is probably related to the presence of the weak evaporitic Hormuz Series that prevents the occurrence of very large aseismic motion. According to the values of geodetic moment rates in the Zagros sub-zones and based on the value of the released seismic energy in the north and northeast part of the study area, it seems that in the future, the most of the seismic potential energy and seismic hazard are in the southeastern part of Zagros belt in Fars and Bandar Abbas hinterland and a part of Khuzestan sub-zone. Our study has implications for better comprehending the current seismotectonic pattern of Zagros fold and thrust belt as an evolving deformation area.

When an earthquake occurs, a part of the released energy is propagated in the form of elastic waves at a speed that depends on the nature of the propagation environment. The radiated energy from earthquake focus in all directions is called radiation pattern and depends on the fault mechanism. The environment response to longitudinal waves appears as compression and expansion of the environment. This can affect on water levels in aquifers, wells and springs before, during and after the event. The changes of the groundwater levels caused by an earthquake are important with respect to other induced parameters; they may generate crustal deformations, affect on water supplies and production of oil wells, initiate liquefaction, control the distribution of aftershocks, trigger earthquakes and mud volcano eruptions. In this study, the effect of April 2013 Kaki earthquake (Mw6.3) on water levels in wells located in a range of 50 km radius around the earthquake epicenter was compared in successive months in the preceding years, during and after the event. Regarding the earthquake focal mechanism and using the estimated tensile and compressive zones in the study area, the correlation of these areas with changes in water levels and discharge of wells and springs was examined. The results of evaluations indicate that the water levels in wells rose and the discharge of the wells and springs located within the radiation range of the pressure waves increased after the earthquake. The wells located in the direction of compressive radiation showed a level of elevation. In contrast, wells located along the shear strain either experienced a drop in water level or had no significant changes. The results show that there is compatibility between the pattern of seismic waves and the changes in the water levels in wells and springs. Because of the difference in characteristics of geological formations, the response of the wells located in the same seismic pattern may not be the same. On the other hand, since the earthquake occurred in the low rainfall time, changes in water levels cannot be caused by rainfall. Field data shows other recorded effects such as the recovery of the springs of Kale and Seyyed Ali which indicates the increase in discharge of water in the region. The liquefaction created in the area is a reason for the passage of a compressive wave that has led to increase of water levels in the wells. The amount of decrease or increase in water level depends on the magnitude and distance to hypocenter of the earthquake and geological characteristics of the well. The water level in the well located in Shonbe village (28.34°N, 51.76°E) increased 1.6 m after the earthquake.