Santosh Panda

Remote sensing observations of pre‐earthquake thermal anomalies in Iran

Stresses acting before an earthquake in tectonically active regions can augment the near ground temperature of the region. Such changes detected through thermal remote sensing can provide important clues about future earthquakes. A post‐earthquake analysis through NOAA‐AVHRR data showed pre‐earthquake thermal anomalies prior to the Bam earthquake on 26 December 2003 and the Dahoeieh‐Zarand earthquake on 21 February 2005 in Iran. It was observed in these earthquakes that there was short‐term temporal increase in land surface temperature (LST) of the regions around the epicenters. The rise in temperature was about 5–10°C. Further, temperature variation curves prepared from air temperature data collected from several meteorological stations around epicentres confirmed the appearance of thermal anomalies prior to several earthquakes between February and March 2005 in Iran. The thermal anomalies went away along with the earthquake events. Release of greenhouse gases from rocks due to the induced pressure before earthquakes can create a localized greenhouse effect. Charge carriers in rocks can be free electrons, which dissociate under high pressure. When they again recombine to attain electron stability they release heat, which can increase the LST of the region.

MODIS land surface temperature data detects thermal anomaly preceding 8 October 2005 Kashmir earthquake

During the morning (03:50:40 UTC) of 8 October 2005 a major (M w 7.6) shallow focus (26 km) earthquake struck Kashmir (Himalayan region). Its epicentre was located 10 km NNE of Muzaffarabad (USGS 2005, Magnitude 7.6—Pakistan, available online at http://earthquake.usgs.gov/eqcenter/eqinthenews/2005/usdyae/). The present manuscript is an attempt to study the development of thermal anomaly in land surface temperature (LST) preceding this earthquake. Using data from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard National Aeronautics and Space Administration (NASA) Terra satellite, the daily daytime LST images have been analysed for the correlation between LST variations and Kashmir earthquakes. An evident correlation of thermal anomaly in LST that is apparently related to pre‐seismic activity has been identified. An attempt has also been made to quantify the change in LST (in °C) with reference to previous day temperature values and background data (MODIS LST data from 2000–2004). A 4–8°C rise in LST to the south of the earthquake epicentre has been observed seven days before the major event. Air temperature data from two meteorological stations (Islamabad and Srinagar) also supports the observations made through MODIS LST data. The role of terrain parameters like rock types, vegetation and topography upon the spatial and temporal variations of anomalous temperature area have been studied.

Remotely Sensed Active Layer Thickness (ReSALT) at Barrow, Alaska Using Interferometric Synthetic Aperture Radar

Active layer thickness (ALT) is a critical parameter for monitoring the status of permafrost that is typically measured at specific locations using probing, in situ temperature sensors, or other ground-based observations. Here we evaluated the Remotely Sensed Active Layer Thickness (ReSALT) product that uses the Interferometric Synthetic Aperture Radar technique to measure seasonal surface subsidence and infer ALT around Barrow, Alaska. We compared ReSALT with ground-based ALT obtained using probing and calibrated, 500 MHz Ground Penetrating Radar at multiple sites around Barrow. ReSALT accurately reproduced observed ALT within uncertainty of the GPR and probing data in ~76% of the study area. However, ReSALT was less than observed ALT in ~22% of the study area with well-drained soils and in ~1% of the area where soils contained gravel. ReSALT was greater than observed ALT in some drained thermokarst lake basins representing ~1% of the area. These results indicate remote sensing techniques based on InSAR could be an effective way to measure and monitor ALT over large areas on the Arctic coastal plain.

Technical Note: Mapping and forecasting of North Indian winter fog: an application of spatial technologies

In India, the Indo‐Gangetic plain (part of Northern India) is invariably affected by dense fog in the winter months every year due to typical meteorological, environmental and prevailing terrain conditions. Pollution also plays an important role in the formation of fog (smoke+fog = smog) in India. Using National Oceanic and Space Administration‐advanced very high resolution radiometer data the fog‐affected regions in Northern India were delineated and the spatial extent of fog for the winter months of the years 2002–03, 2003–04 and 2004–05 (December–February) were studied and mapped. Forecast for future fog based on the analysis of satellite and meteorological (air temperature, relative humidity and wind speed) data was also done. The fog‐affected areas were classified into maximum‐fog‐affected area, moderately fog‐affected area and least fog‐affected area. It has been found that in the winter months of the years 2002–03, 2003–04 and 2004–05, the fog‐affected area in Northern India was about 867 000 km2, 625 000 km2 and 706 800 km2 respectively. The maximum fog‐affected area was found to be 606 400 km2, the moderately fog‐affected area was found to be 230 400 km2 and the least fog‐affected area was found to be 404 500 km2. Further, based on meteorological parameters, such as temperature, humidity and wind speed along with elevation data was used to derive an approach for future fog prediction in this region.

Satellite data in a rapid analysis of Kashmir earthquake (October 2005) triggered landslide pattern and river water turbidity in and around the epicentral region

The Kashmir earthquake of 8 October 2005 that epicentred 10 km northeast of Muzaffarabad town caused widespread slope failures (landslides) extending from Balakot in the northwest to Khudpura in the southeast through Muzaffarabad and Kuroli, with the slides concentrated mostly along the river valley. The southeasterly (sun‐facing) hill slopes were affected predominantly. These landscape changes and the sudden increase in turbidity in the Neelam River have been delineated on earth‐observing satellite data. The occurrence of the landslides is observed linearly along a NW–SE line extending for about 40 km in and around the epicentral zone. From the damage pattern it is deduced that this linear zone might be the maximum displaced block during the earthquake, generated by reverse thrusting.

Dissolved organic matter composition of Arctic rivers: Linking permafrost and parent material to riverine carbon

Recent climate change in the Arctic is driving permafrost thaw, which has important implications for regional hydrology and global carbon dynamics. Permafrost is an important control on groundwater dynamics and the amount and chemical composition of dissolved organic matter (DOM) transported by high-latitude rivers. The consequences of permafrost thaw for riverine DOM dynamics will likely vary across space and time, due in part to spatial variation in ecosystem properties in Arctic watersheds. Here we examined watershed controls on DOM composition in 69 streams and rivers draining heterogeneous landscapes across a broad region of Arctic Alaska. We characterized DOM using bulk dissolved organic carbon (DOC) concentration, optical properties, and chemical fractionation and classified watersheds based on permafrost characteristics (mapping of parent material and ground ice content, modeling of thermal state) and ecotypes. Parent material and ground ice content significantly affected the amount and composition of DOM. DOC concentrations were higher in watersheds underlain by fine-grained loess compared to watersheds underlain by coarse-grained sand or shallow bedrock. DOC concentration was also higher in rivers draining ice-rich landscapes compared to rivers draining ice-poor landscapes. Similarly, specific ultraviolet absorbance (SUVA254, an index of DOM aromaticity) values were highest in watersheds underlain by fine-grained deposits or ice-rich permafrost. We also observed differences in hydrophobic organic acids, hydrophilic compounds, and DOM fluorescence across watersheds. Both DOC concentration and SUVA254 were negatively correlated with watershed active layer thickness, as determined by high-resolution permafrost modeling. Together, these findings highlight how spatial variations in permafrost physical and thermal properties can influence riverine DOM.

Remote Sensing of River Erosion on the Colville River, North Slope Alaska

The Colville is an Arctic river in the Alaska North Slope. The residents of Nuiqsut rely heavily on the Colville for their subsistence needs. Increased erosion has been reported on the Colville, especially along bluffs, which shaped the goals of this study: to use remote sensing techniques to map and quantify erosion rates and the volume of land loss at selected bluff sites along the main channel of the Colville, and to assess the suitability of automated methods of regional erosion monitoring. We used orthomosaics from high resolution aerial photos acquired in 1955 and 1979/1982, as well as high resolution WorldView-2 images from 2015 to quantify long-term erosion rates and the cubic volume of erosion. We found that, at the selected sites, erosion rates averaged 1 to 3.5 m per year. The erosion rate remained the same at one site and increased from 1955 to 2015 at two of the four sites. We estimated the volume of land loss to be in the magnitude of 166,000 m3 to 2.5 million m3 at our largest site. We also found that estimates of erosion were comparable for manual hand-digitized and automated methods, suggesting our automated method was effective and can be extended to monitor erosion at other sites along river systems that are bordered by bluffs.

Estimating active layer thickness and volumetric water content from ground penetrating radar measurements in Barrow, Alaska

Ground penetrating radar (GPR) has emerged as an effective tool for estimating active layer thickness (ALT) and volumetric water content (VWC) within the active layer. In August 2013, we conducted a series of GPR and probing surveys using a 500 MHz antenna and metallic probe around Barrow, Alaska. We collected about 15 km of GPR data and 1.5 km of probing data. Here, we describe the GPR data processing workflow from raw GPR data to the estimated ALT and VWC. We include the corresponding uncertainties for each measured and estimated parameter. The estimated average GPR‐derived ALT was 41 cm, with a standard deviation of 9 cm. The average probed ALT was 40 cm, with a standard deviation of 12 cm. The average GPR‐derived VWC was 0.65, with a standard deviation of 0.14.