مهندس حمیدرضا نانکلی

The Makran subduction zone from the point of view of Tectonics, and seismicity is really interesting  for researchers. The Makran zone is divided into two parts of western Iran and east in Pakistan. The largest earthquake of the last half century, with magnitude 7.8 in 2013, occurred near the city of Saravan. The occurrence of this earthquake indicates the locks on the western Makran border with the eastern Makran. But there is still the possibility of silent earthquake in that area. Determination of the displacement Iranian Permanent GPS Network for Geodynamics is of particular importance in Makran's behavioral structure. In this study, in order to determine the displacement of this earthquake coherent earthquake, observations of the Iranian Permanent GPS of the geodynamic network of the country called Saravan, Golmorti, Zabol and Fahraj were collected, processed and analyzed in the time interval of the earthquake. With a view to better approximation and symmetry in a fitted math model, an 14-month interval was considered that the earthquake was in the middle of the range. Also, the GAMMIT &GLOBK software was used to process GPS data. According to the results, the actual viable displacement vectors are 55.78 mm in diameter and the model is up to 50.15 mm in length for the Saravan station with the largest displacement, respectively, Golmorti  3.03 mm and Zabol 2.70 mm and Fahraj 1.19 mm. They showed displacement. Given the residual values ​​at Saravan station and visual analyzes, first degree polynomials were fitted for two periods before and after the earthquake. The changes in the Flat component and altitude components are a function of the fault mechanism, the depth of the lock, and the intervals of the points from the fault. The maximum change in the altitude component of the Fahraj Station is 24.12 millimeters, which is likely to be related to other geological phenomena. In the case of other stations, Golmorti with a height of 5.5 mm, Saravan 2.75 mm lower elevation and Zabol with 1.8 mm lower altitude has been associated.

Agricultural drought is one of the most complex natural disasters. Due to spatial and temporal variations This phenomenon needs to improve the information and tools available to monitor this phenomenon on all scales. Remote sensing data and GIS, An appropriate monitoring tools to assess the extent and severity of droughts available in the villages. Plant growth rate is one of the most important indicator of the occurrence of drought . In this study, a number of plant indices were evaluated and, as a result, the indicator NDVI As appropriate The highest index for vegetation has been selected . In this study, from the images MODIS The resolution right time and place for the province Drought risk analysis have been used. Period covered by the month March to July of the year 2000 20 1 7. First, geometric and radiometric correction images Have. Then by evaluating a seven -year series of images NDVI, SPI, LST, SPEI And the total annual rainfall in the region, the trend of drought changes has been shown. In this study, by using the satellite indices mentioned in Semnan province, the climate of the drought affected area was investigated. Satellite indicators show the effects of drought in Semnan province in 2000 , 2010 , 2013 , 2016 . According to this index in 2000 , 2001, 2006, 2007, 2016, 2017 there has been a drought in the province. Drought severity in 2000 , 2016 More than other years . Also, 2005 is Tersali and other years are the average years . The results showed that identifying drought-sensitive areas could have a very important role in managing the management of drought risk.

Precise Point Positioning (PPP) is a stand-alone positioning technique that is capable to provide real-time centimeter level accuracy for a single receiver using the precise satellite orbit and clock data products. Nowadays, a number of free online PPP processing services have been developed in order to obtain highly accurate coordinates with respect to a well-defined datum. Four examples of these services are: (1) Canadian Spatial Reference System (CSRS-PPP), (2) GPS Analysis and Positioning Software (GAPS), (3) Automatic Precise Positioning Service (APPS) and (4) magicGNSS. This paper aims to investigate accuracy of these four online PPP services in static positioning and zenith tropospheric delays (ZTDs) estimation. To this end, repeatability of these four PPP services is investigated for two International GNSS Service (IGS) stations, namely TEHN located in Iran and SOFI located in Bulgaria, in the period from February 1-15, 2015. The repeatability of horizontal components for APPS, GAPS, magicGNSS and CSRS-PPP services are 3 mm, 5.5 mm, 5 mm and 3 mm, respectively. These values for height components are 5.5, 9.5, 6.5 and 6 mm for APPS, GAPS, magicGNSS and CSRS-PPP services, respectively. Furthermore, for the both IGS stations, the estimated position by using these services were compared with their known coordinates in ITRF2008. The results showed that precision of horizontal components obtained by these online PPP services are at a sub-centimeter level, which is required for many mapping applications. Finally, the ZTDs estimated using four online PPP services were compared for February 1, 2015. Compared with the corresponding values published on the IGS Web site, the precision of ZTDs estimated by APPS, GAPS, magicGNSS and CSRS-PPP are 3 mm, 4 mm, 3 mm and 5 mm, respectively.

GPS time series consists of a linear trend, harmonic signals, probable offsets and also noise which is described as a stochastic part. Because of various applications of GPS time series such as plate tectonics, crustal deformation and earthquake dynamics studies, these time series should be modeled with high accuracy. For this purpose, systematic effects in functional model should be determined with high accuracy. In this paper the effect of earthquakes is also considered in the functional model in addition to mentioned behaviors. Because earthquakes cause crustal deformations, their effects can be observed in the shape of offsets (as coseismic effects) and (or) rate changes (as coseismic or postseismic effects) in the time series. Neglecting these effects lead to biased estimation of noise amplitudes. To discover the effect of earthquakes, a manual solution is used for each station. Effects are detected graphically by comparison of behavior of time series and epoch of occurred earthquakes in the region. The earthquakes which considering their effects, lead to the best fitting of functional model to time series, are selected as effective ones. Because the Alborz range is the most seismically active region in the Northern Iran, 25 permanent GPS stations with the time span between 2005 and 2013 in this area are selected for this study. Analysis of time series indicates similar behavior of time series with the same offset times and common earthquake effects for most stations (also for those which are located in far distances from epicenters). This result means that systematic effects may propagate from one station to the others during the processing and the network adjustment. Furthermore, noise analysis of time series using least squares (co)variance components estimation method, shows that neglecting seismic effects can result in the presence of random walk noise in 88%,12% and 60% of north, east and up components, respectively. However, considering the seismic effects causes positive estimation of variances of random walk noise in 12%,12% and 36% of north, east and up components, respectively. Finally, due to similar behavior of time series, a reprocessing of them could be suggested.

The Alborz range of northern Iran is a region of active deformation within the broad Arabia–Eurasia collision zone. The range is also an excellent example of coeval strike-slip and compressional deformation, and as such can be an analogue for inactive fold and thrust belts thought to involve a component of oblique shortening. It is roughly 600 km long and 100 km across, running along the southern side of the Caspian Sea. Several summits are 4000 m in altitude. Damavand, a dormant volcano, reaches 5671 m. The highest non-volcanic summit is Alam Kuh, at 4830 m.
The Alborz range, northern Iran, deforms by strain partitioning of oblique shortening onto range-parallel left-lateral strike-slip and thrust faults. Deformation is due to the north–south Arabia–Eurasia convergence, and westward motion of the adjacent South Caspian relative to Iran. The occurrence of moderate to large earthquakes in the Alborz suggests an important deformation regime in this mountain belt. This belt has been responsible for several catastrophic earthquakes in the past. The Manjil earthquake of 20 June 1990, which is the most disastrous Iranian earthquake in the twentieth century, occurred in this belt. Both thrust and strike-slip faulting have been reported in this belt.
By the knowledge of the crustal deformation characteristics in areas with active tectonics we can realize the style, direction and magnitude of the deformation in the area, it can contribute to the deeper understanding of the underlying tectonic processes and to the improvement of the seismic hazard assessment.
In this contribution strain rate fields (using geodetic data vs. seismic data) calculated over the three different parts of Alborz regions (Western, Central, and Eastern Alborz). Eigenspace components of seismic strain tensor (seismic events with Ms ≥ 4.0 in the time interval 1900–2010) over three zones revealed crustal shortening over all three zones. Namely, the results of seismic data showed left-lateral strike-slip faulting in the Eastern Alborz, the right-lateral strike-slip motion in the Western Alborz and compression mechanism in the Central zone. The highest compressional rate in the Western Alborz probably represent the high seismicity rate of this region. In comparison, eigenspace components of geodetic strain tensor (during time interval from 2005 to 2009) illustrated high rate of compressional components in the Central and Western zones. Comparison of seismic and geodetic strain rates in the Western Alborz indicates the deformation rate over this region is associated with seismic activities. However, in Central and Western regions the geodetic strain rates appeared remarkably larger than seismic strain rates. May, this fact illustrated the deformation pattern in these regions are related to the local aseismic creep of those segments. The difference between eigendirection of both kind of tensors (geodestic vs. seismic) in segments probably were related to the short period of GPS data with respect to the seismic data. However, it is a fact that early historical data are incomplete. So, the catalog completeness is crucial for estimating reliable seismicity strain rates and, consequently, for use in seismic hazard assessments. Hence, the performing the repeated geodetic data over the Alborz region is proposed to investigate the reliable estimating of the strain rate.

In the 11th August 2012 two Earthquakes trembled Azarbayjan that their scales were 6 Mw and 6.2 Mw. The locking depth of these two earthquakes is about 10 km, the epicenter of the first one is 38.55 N and 46.87 E, and the second one is 38.87 N and 46.87 E. In this research displacement of the earth crust during trembling on these stations was determined by using permanent GPS stations in Ahar Earthquake 2012. The cosiesmic offset due to the Ahar earthquake has been studied using permanent GPS Network of Azarbayjan (a sub network of Iranian permanent GPS Network). Here, we explore these issues using data processing and times series analysis of the GPS sites. We found 0.5 to 2 cm offset that the GPS site (near and far) showed from the main rapture due to earthquake.

During the recent years, GPS has been introduced as a unique tool to study the propagation of electromagnetic waves through the atmospheric layers, in particular the ionosphere. The ionosphere is currently the major source of errors in GPS positioning which its effect on wave propagation is dependent on the amount of TEC and signal frequency. In this paper, the temporal-spatial variations in Iranian TEC has been studied using observations of 40 IPGN stations. For this purpose, GPS observation data, consisting 10 days in 2012 and 3 days in 2013 which are the first days of solar months, have been processed via Bernese 5.0 GPS software (first days of each season is included in our data). To do so, regional ionosphere modeling, estimation of TEC values and calculation of the receiver DCB have been performed by expansion of spherical harmonic functions up to the sixth degree and order. Furthermore, the difference between smoothed code observations from the first and second frequencies has been used to eliminate geometric effects, such as satellite and receiver clock biases and tropospheric delays. Blunder and cycle slip detection as well as code observation smoothing have been performed during preprocessing steps. The results have shown that the maximum and minimum ionosphere effects are related to the spring and winter seasons, respectively, and the maximum TEC value occures at about 14:00 local time. Moreover, we can see significant TEC variations in accordance with changes in latitude. on the other hand, the maximum and minimum TEC values in Iran is associated with the minimum and maximum latitudes, respectively. In the spring of 2012, 100 TECU was observed as the TEC value. If the satellites are near the horizon and by using second frequency, It could lead to an error 75 meters on the satellite–receiver range.

In previous decades, using traditional geodetic observations such as distance and angle measurements was prevalent in the earth surface displacement studies. After accessing to satellite positioning systems with a high precision ability such as GPS, we encountered to an upheaval in the earth surface displacement studies. Indeed using temporal variations of the earth surface deformation, the seismotectonics of the area can be distinguished. Deformation modeling of the area can be accessed using the analyzing of repeated geodetic measurements. In Tehran area the earthquake studies is an important task and in this paper we are going to use GPS measurements for this field. Here 35 GPS stations cover whole of Tehran which consists North Tehran fault. These stations were occupied at least 2 annual epochs and some of them were measured more than 4 times. After processing the acquired data and analyzing the results, the velocity field was obtained. Deformation analysis of the velocity field shows a small left lateral movement about 0.5-2 mm/year and more or less the same value for shortening in the northern band Tehran area. This value is not constant along the northern band and it seems the eastern part where we reach the Mosha fault the deformation is more significant than western part. The observed rate is equal to a total movement of ~5km during 2.5-10 my which is consistent with geological studies carried out in this area.

We present the results of continuous GPS measurements to interpret present-day kinematic along and across northern Iran (i.e. the Alborz mountain range and northern part of Central Iranian Block (CIB)). In this study velocity field and geodetic strain rate of 30 CGPS stations

A three-dimensional lithosphere model with horizontal dimensions of 1500 km×600 km and a depth extent of 70 km for the Zagros is constructed from available geophysical data to find out strength of the outermost layers in this area. The structural boundaries of the model are based on the results from the deep seismic sounding profiles. First the finite element model for the temperature is solved in order to obtain initial temperature and the geotherm، after that structural viscoelastic problem is solved using the same mesh as in the thermal initial condition. Preliminary results for wet and dry rheology indicate that the depth of the BDT is about 8 km and 11 km for hot geotherm and 10. 5 km to14 km for cold geotherm. The results are in good agreement with focal depth in the Zagros that most earthquakes occur in 8 to 15 km depth (Tatar et al.، 2004 and Jackson et al.، 2008)، that the long-term strength of the continental lithosphere resided only in its upper part، which was contained wholly within the crust.