Daily Rainfall Forecasting Models using ANN and ELM for Development of Rainfall Threshold based Landslide Early Warning System

Renuga Devi S., Venkatesh C. and Arulmozhivarman P.

The present study aims to forecast rainfall intensity on a daily basis which could be used as an input to a rainfall threshold based landslide early warning system. The study area is Coonoor, a potential site of landslides, located in Nilgiris district of Tamil Nadu, India. Artificial neural network (ANN) and extreme learning machine (ELM) models are developed to forecast rainfall intensity one day in advance and their performance is compared. The input data set for the predicting models comprises of rainfall intensity, minimum and maximum temperature, cloud cover, wind speed and relative humidity were recorded on a daily basis at Coonoor observatory for a period of 10 years. The study also computes the risk of landslide occurrence by comparing the predicted rainfall intensity with the rainfall threshold for the study area. The performance of the forecasting models was evaluated using standard performance evaluation measures- mean square error (MSE), correlation coefficient (CC) and time taken for convergence. The results obtained confirm the suitability of both ANN and ELM models for the task of rainfall forecasting applied to landslide prediction.

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Geological and petrological mapping in and around Kallambalam, Trivandrum, Kerala

Aju C. D. and Raicy M. C.

The Kerala Khondalite Belt, southern Kerala is known to be a part of the granulite facies matapelites of Proterozoic age. The present study focuses to map the geological characteristics in and around Kallambalam, Trivandrum district, Kerala. Extensive field investigations were carried out and rock specimens were collected from the field for laboratory investigations. Thin sections were prepared at the laboratory and the optical and mineralogical properties were investigated under polarized microscope. The major rock types identified in the area are garnetiferrous biotite gneiss, charnockite and khondalite and minor rock types are pyroxene granulite and laterites. Incipient charnockitisation was also noticed at Kattuchantha which is an indication of paleofluid channels in the rocks. Structural features such as veins of quartzite and pegmatite, joints and foliations in garnet biotite gneiss were also observed in the study area. Intense foliations of dark colored and light colored minerals were present in rocks which indicate deformation suffered by different types of rocks. The present study reveals that the rocks present in the area indicate high grade metamorphic facies probably of upper ambhibolite to granulitic facies.

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Seismic liquefaction hazard zonation and contour maps for Mumbai city using open source GIS

Phule-Raskar Reshma and Choudhury Deepankar

Recent destructive earthquakes have demonstrated soil liquefaction hazards and corresponding structural disasters across the world. The local and geologic soil conditions have a great influence on the amplification of earthquake ground motions which may result into serious seismic liquefaction hazards which is site-specific. In this paper, geographical information systems (GIS) based seismic soil liquefaction studies for financial capital of India, Mumbai city have been carried out to develop liquefaction hazard map and contours to minimize earthquake liquefaction disasters. Deterministic procedures for estimating the factor of safety (FSL) against liquefaction for cohesionless soils in Mumbai city have been carried out by considering site-specific in-situ soil properties. A comparative study shows the need and suitability of such procedure. Estimated seismic liquefaction hazards in various locations of Mumbai city are mapped including the contours by using the open source software, Quantum GIS (QGIS). The maps are produced by using the inverse distance weightage (IDW) method of interpolation. The developed liquefaction hazard zonation maps can be used effectively by the engineers and planners as first-hand information for seismic liquefaction hazard mitigation in Mumbai city.

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A review on the tectonic setting and seismic activity of the Shillong plateau in the light of past studies

Baro Olympa and Kumar Abhishek

The Shillong Plateau originated due to the movement in the faults surrounding it; however which fault caused the uplift of the plateau is debatable. Several earthquakes have occurred in the plateau due to these surrounding faults. One such earthquake is the Assam earthquake of 1897 (Mw=8.1). Also, there are evidences that similar earthquakes had occurred prior to 1897. In the light of the partial evidences, the return period of such great earthquakes remains uncertain. Further, several research studies had also highlighted the damages evidenced in the Shillong Plateau during many of the past earthquakes. The location and mechanism of such earthquakes however were observed in a variety of ways by different researchers. This paper presents a detailed review on the different opinions about the origin of the Shillong Plateau as well as the location and orientation of the faults surrounding it. Further, a detailed discussion on the devastations caused by past earthquakes in terms of geological changes, structural damages and loss of life during each of the past earthquakes is done. This study highlights the need for detailed regional studies to be conducted in the Shillong Plateau filtering out the different opinions by various researchers such that ongoing seismicity can be considered for future studies.

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