Exposing the urban continuum: implications and cross-comparison from an interdisciplinary perspective

ABSTRACT

There is an increasing availability of geospatial data describing patterns of human settlement and population such as various global remote-sensing based built-up land layers, fine-grained census-based population estimates, and publicly available cadastral and building footprint data. This development constitutes new integrative modeling opportunities to characterize the continuum of urban, peri-urban, and rural settlements and populations. However, little research has been done regarding the agreement between such data products in measuring human presence which is measured by different proxy variables (i.e. presence of built-up structures derived from different remote sensors, census-derived population counts, or cadastral land parcels). In this work, we quantitatively evaluate and cross-compare the ability of such data to model the urban continuum, using a unique, integrated validation database of cadastral and building footprint data, U.S. census data, and three different versions of the Global Human Settlement Layer (GHSL) derived from remotely sensed data. We identify advantages and shortcomings of these data types across different geographic settings in the U.S., which will inform future data users on implications of data accuracy and suitability for a given application, even in data-poor regions of the world.     

Identifying vulnerable areas of aquifer under future climate change (case study: Hamadan aquifer,West Iran)

Groundwater is the main source of water in arid and semi-arid regions, so it is very important to recognize vulnerable parts of aquifer under future climate change conditions. In this research, 16 climate models were evaluated based on weighting approach. HADCM3 and CGCM2.3.2a models were selected for temperature and precipitation prediction, respectively. LARS-WG was used for downscaling AOGCMs outputs. Results show that temperature increase by 1.4 °C and precipitation changes between +10 and ?6 % under B1 and A2 emission scenario, respectively. Runoff volumes will decrease by ?39 % under A2 emission scenario whereas runoff volume will increase by +12 % under B1 emission scenario. Simulation of groundwater head variation by MODFLOW software indicates higher groundwater depletion rate under A2 scenario compared to B1 scenario. Groundwater model outputs indicate that the most vulnerable part of the aquifer is located in the southwest region. Large number of extraction wells and low aquifer transmissivity are the reasons for high vulnerability of the region.     

Performing the power spectrum-area method to separate anomaly from background for induced polarization data: (a case study; Hamyj copper deposit,Iran)

Anomaly separation plays a critical role in mineral exploration. The power spectrum-area considers the spatial data which give rise to detecting the anomalies more significantly. Induced polarization data has been surveyed using dipole-dipole array in the Hamyj copper index. Electrode spacing was designed at about 20 m. The Hamyj index was explored based on the result of remote sensing and economic geology. Hamyj deposit is located about 80 km west of Birjand city, South Khorasan province, Iran. In this paper, the induced polarization from the concentration-place domain was transferred to the time-frequency domain by using two dimensional Fourier transforms in order to use the power spectrum-area method. Then, the power spectrums of induced polarization signals were calculated and differentiated by means of fractal geometry. The threshold of separation for the design of digital filter was used to filter the data. Threshold IP and filtered data was calculated by concentration-area method. Finally, IP data and filtered data were compared with each other and 72 percentages of the anomalous data corresponded significantly with each other. The results showed that the power spectrum-area method can eliminate noise; hence, anomalies can be highlighted more sharply. As far as this study is concerned, this method can be used to suggest the best places for drilling.     

Application of Electrical Resistivity Imaging for Engineering Site Investigation. A Case Study on Prospective Hospital Site,Varamin, Iran

The article addresses the application of electrical resistivity imaging for engineering site investigation in Pishva Hospital, Varamin, Iran. Some aqueduct shafts exist in the study area backfilled by loose materials. The goals of this study are to detect probable aqueduct tunnels and their depth, investigate filling quality in the shafts as well as connection(s) between them. Therefore, three profiles were surveyed by dipoledipole electrode array. Also, to investigate the potentially anomalous areas more accurately, five additional resistivity profiles were measured by a Combined Resistivity Sounding-Profiling array (CRSP). According to the results of 2-D inversion modelling, a main aqueduct tunnel was detected beneath the central part of the site. Finally, the resistivity pattern of the detected aqueduct system passing the investigated area was provided using the obtained results.     

Investigation of rock quality of Shirinrud dam site by engineering seismology

At this paper, we studied about the rock quality of Shirinrud dam site by engineering seismology. Shirinrud dam site is located 80 km far from Kerman and 18 km far from Hojadk village. The dam and its constructions are established in the Bidu Formation which consists of seven rock units, and the refraction profiles were surveyed on Jb_3/2, Jb₄, and Jb₅ rock units. To evaluate the rock mass quality and basement topography at this site, nine refraction seismic profiles by primary waves and two refraction seismic profiles by secondary waves were surveyed. We used some methods such as Palmer method, the reciprocal method, plus–minus method, etc. to process and interpret data. Based on investigations, primary wave velocity in unit Jb_3/2 varies between 2,100 and 2,200 m/s, in unit Jb₄ is between 2,100 and 4,200 m/s, and in unit Jb₅ is between 2,500 and 3,000 m/s. The Q values on these three units are 0.05, 1.2, and 1.9, and the rock mass rating (RMR) values are 27.1, 40.5, and 33.5, respectively. With respect to wave velocity, Q, and RMR values, the units Jb_3/2, Jb₄, and Jb₅ are evaluated as very weak, intermediate, and weak, respectively.     

Application of integrated geoelectrical methods in Marand (Iran) manganese deposit exploration

This paper addresses the application of integrated geoelectrical methods including induced polarization (IP), resistivity (RS), and self-potential (SP) for exploration and evaluation of the Marand (Iran) manganese deposit. The SP method was used for reconnaissance, in which five profiles were designed and surveyed with a reference electrode that was placed in a distance of at least 800 m far from the measurement points. For the conduct of RS and IP, a new array proposed by Ramazi (2005a), named combined resistivity profiling and sounding (CRSP) was used along nine profiles that made it possible to do sounding survey and produce apparent resistivity pseudo-sections. Some anomalies were detected by means of SP surveys along the profiles and some other were located from IP and RS pseudo-sections, and there was good consistency between anomalies detected by IP and RS and SP method. To check the efficiency of CRSP and in comparison with dipole–dipole array, in the location of profile no. 6, a profile with the dipole–dipole array was designed and surveyed. Finally, by integration of the results from the geoelectrical methods, some locations were suggested for borehole drilling. After drilling in those locations, cores were studied and compared with the results obtained from the geoelectrical methods that resulted in confirmation of the geoelectrical findings. The results obtained by the CRSP array have a match better than the drilling results.     

Measuring sheet erosion using synthetic color‐contrast aggregates

The bulk of eroded soils measured at the outlets of plots, slopes and watersheds are suspended sediments, splash‐induced sheet erosion. It is depending on rainfall intensity and antecedent soil moisture contents and contributes to a significant proportion of soil loss that usually is ignored in soil erosion and sediment studies. A digital image processing method for tracing and measuring non‐suspended soil particles detached/transported by splash/runoff was therefore used in the present study. Accordingly, fine mineral pumice grains aggregated with white cement and coloured with yellow pigment powder, with the same size, shape and specific gravity as those of natural soil aggregates, called synthetic color‐contrast aggregates, were used as tracers for detecting soil particle movement. Subsequently, the amount of non‐suspended soil particles detached and moved downward the slope was inferred with the help of digital image processing techniques using MATLAB R2010B software (Mathworks, Natick, Massachusetts, USA). The present study was conducted under laboratory conditions with four simulated rainfall intensities between 30–90 mm h^‐1, five antecedent soil moisture contents between 12–44 % v v^‐1 and a slope of 30%, using sandy loam soils taken from a summer rangeland in the Alborz Mountains, Northern Iran. A range of total transported soil between 90.34 and 1360.93 g m^‐2 and net splash erosion between 36.82 and 295.78 g m^‐2were observed. The results also showed the sediment redeposition ratio ranging from 87.27% [sediment delivery ratio (SDR) = 12.73%] to 96.39% (SDR = 3.61%) in various antecedent soil moisture contents of rainfall intensity of 30 mm h^‐1 and from 80.55% (SDR = 19.45%) to 89.42% (SDR = 10.58%) in rainfall intensity of 90 mm h^‐1. Copyright © 2013 John Wiley & Sons, Ltd.     

Application of geostatistical simulation to compile seismotectonic provinces based on earthquake databases (case study: Iran)

This article is devoted to application of a simulation algorithm based on geostatistical methods to compile and update seismotectonic provinces in which Iran has been chosen as a case study. Traditionally, tectonic maps together with seismological data and information (e.g., earthquake catalogues, earthquake mechanism, and microseismic data) have been used to update seismotectonic provinces. In many cases, incomplete earthquake catalogues are one of the important challenges in this procedure. To overcome this problem, a geostatistical simulation algorithm, turning band simulation, TBSIM, was applied to make a synthetic data to improve incomplete earthquake catalogues. Then, the synthetic data was added to the traditional information to study the seismicity homogeneity and classify the areas according to tectonic and seismic properties to update seismotectonic provinces. In this paper, (i) different magnitude types in the studied catalogues have been homogenized to moment magnitude (M_w), and earthquake declustering was then carried out to remove aftershocks and foreshocks; (ii) time normalization method was introduced to decrease the uncertainty in a temporal domain prior to start the simulation procedure; (iii) variography has been carried out in each subregion to study spatial regressions (e.g., west-southwestern area showed a spatial regression from 0.4 to 1.4 decimal degrees; the maximum range identified in the azimuth of 135?±?10); (iv) TBSIM algorithm was then applied to make simulated events which gave rise to make 68,800 synthetic events according to the spatial regression found in several directions; (v) simulated events (i.e., magnitudes) were classified based on their intensity in ArcGIS packages and homogenous seismic zones have been determined. Finally, according to the synthetic data, tectonic features, and actual earthquake catalogues, 17 seismotectonic provinces were introduced in four major classes introduced as very high, high, moderate, and low seismic potential provinces. Seismotectonic properties of very high seismic potential provinces have been also presented.     

Compiling and verifying 3D models of 2D induced polarization and resistivity data by geostatistical methods

A 3D model of collected time-domain induced polarization (IP) and electrical resistivity tomography (ERT) data is compiled by geostatistical methods as well as studying spatial correlation among the database. Mesgaran copper deposit, located in Birjand eastern Iran, was chosen to compile and verify the model, leading to five parallel surveyed IP and ERT profiles with dipole–dipole arrays. The collected data were inverted, and then 2D models of IP and ER were prepared; also 3D inversion was done. Afterward, the 3D model has been built by geostatistical methods. Correspondingly, the anomalies threshold was detected by fractal methods and the estimation variance and Kriging efficiency were calculated to validate the modeling. The mineralization zones were determined according to the classified anomalies and those with the lowest error. Results indicated a high correlation between anomalies identified from the model and mineralization. The results made it possible to construct 3D models from surveyed 2D data with acceptable error level.