Site amplification characteristics and seismic energy levels at four electrical substations

Kim Jun Kyoung and Oh Tae Seok*

Seismic design criteria have not reflected site-specific characteristics in Korea appropriately; many problems have been pointed out including that site-specific response spectra using observed accelerations in the high-frequency range are relatively higher than the national seismic design criteria. Various methods have been suggested for investigating site amplification characteristics with H/V spectral ratios using only the acceleration motion of one station being applied in this study, to three kinds of seismic energy: S waves, Coda waves and background noise. The H/V spectral ratios of these three kinds of seismic energy were investigated simultaneously at four electrical substations. The four substations had each been fitted with a seismic sensor and the acceleration data for three macro earthquakes observed simultaneously at the four sites over a limited time period were used in the H/V spectral ratios.

In total, 36 ground motions (24 horizontal and 12 vertical components) from three macro earthquakes, 3.4 or higher in local magnitude (ML; the Odaesan, Jeju and Gongju earthquakes) were used. The H/V spectral ratios of the S waves, Coda waves and background noise were compared. All four of the electric substations showed consistent H/V spectral ratios for S waves, Coda waves and background noise over a wide frequency band. The site amplification characteristics at the low and high frequency range, as well as the specific resonance frequency of each electric substation, varied; this suggests that there are unique amplification characteristics at each substation. Regarding resonance frequency, the sites were commonly classified as SB or harder rocks.

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Assessment of liquefaction potential of Guwahati city based on geotechnical standard penetration test (SPT) data

Singnar Longbir and Sil Arjun*

Soil liquefaction is the failure or loss of shear strength of the cohesionless soil due to the sudden increase in pore water pressure causing the effective stress in the soil to reduce significantly due to an earthquake shaking. The Guwahati city in Assam is located in the Northeastern region (NE) of India and the whole region is considered to be the most seismically active zones in the country as well as globally in sixth position. There have been several major and great earthquakes in the past such as 1897 and 1950 earthquakes having magnitude Mw>8.0. The soil deposits of the city mainly consist of an alluvial type of Holocene age. The city has a non-cohesive soil deposit and the shallow ground water table at the various locations.

In this study, an assessment of soil liquefaction potential of Guwahati city was performed based on the method suggested by Youd et al18. The evaluation of liquefaction potential was carried out considering the Great Shillong earthquake of Mw 8.1. A design peak ground acceleration of 0.36g used as the Guwahati city lies in the zone-V of the seismic zoning map of India as per IS 1893(part 1):2002.

In this work, a total of 82 boreholes were collected from the city in such a way that it can cover the whole study area used for the assessment of liquefaction potential, the evaluation reveals that 34 sites are susceptible to soil liquefaction. The factor of safety (FOS) against soil liquefaction was determined for all the sites. The results are presented in the form of contour maps showing FOS against soil liquefaction at several depths. An evaluation of the severity of liquefaction in the form of liquefaction potential index (LPI) was also carried out based on the method proposed by Iwasaki et al.6,17

However, the LPI enables us to ascertain the severity of liquefaction and the results are presented in the form of contour maps at several depths. The present results would be helpful for the city planners, designers and the Govt. of Assam for disaster mitigation strategies.

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Climate Change and Land Revenue: Evidences from Indian Agriculture

Mor Surender

The present study attempts to forecast the impact of climate change on the land revenue for the cultivating of wheat and paddy crops in India. The study employs Ricardian model on cross-section data for the year 2014-2015 for making predictions for land revenue for the year 2100. The findings report that the ongoing process of climatic change has been found affecting land revenue for wheat cultivation as well as paddy cultivation. The results indicate that the land revenue for paddy cultivation is expected to decline by 9 percent, 8 percent and 13 percent while for wheat 10 percent, 7 percent and 11 percent by the year 2020, 2060 and 2100.

It follows from the study that the development of short duration and high heat tolerance varieties of both paddy and wheat crops is the need of the hour. The study advocates a full or partial diversion of crops in designated areas on the basis of agro-climate zones. Therefore, a sort of double-pronged strategy, with one prong aimed at enhancing the land revenue by the development of eco-friendly varieties and the other at reducing the cost of cultivation would be cumulatively effective.

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Constructional Deficiencies in Masonry Structures and Seismic Risk

Adil Dar M.*, Subramanian N., Dar A.R. and Taiyib A. Dar

Most of the buildings in India are masonry structures. Non-engineered masonry buildings are unsafe under strong earthquakes due to their brittle nature. Nearly 60% of India’s entire area is vulnerable to devastating earthquakes. In addition to the main earthquake resistant design code IS-1893, the Bureau of Indian Standards has published IS-13828 for earthquake resistant masonry construction. The Kashmir region of J&K state falls mainly under the severe most seismic zone (i.e. zone V) and the rest falls under zone IV. In the 2005 Kashmir earthquake, about 1329 people lost their lives and 98,000 houses in Kashmir valley were badly damaged.

Post-earthquake investigation was carried out to uncover the causes behind the devastating damage suffered by these structures. Seismically poor architectural design was one of the reasons for such poor performance of these masonry structures. This was being followed by non-engineered construction (without proper structural design) for most of the masonry structures, thus making them highly vulnerable to earthquake failures. Besides the above, poor quality of workmanship coupled with non-engineered construction practices (particularly not strictly following codal earthquake resistant guidelines) was also identified as the main factor. This paper presents the study carried out on two typical public masonry buildings in the Kashmir valley (during their construction phase) to identify the prominent violations of earthquake resistant measures.

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Ecological risk from urbanization in the Karst mountainous region of North China

Wenfei Sheng, Shanzhong Qi and Yetang Wang*

Urbanization in the karst mountainous region of North China has profoundly transformed the spatial pattern of urban land use that has had and continues to have a negative impact on urban karst mountain area. This short communication investigates the possibility of ecological risks in this region owing to land use change such as flood disasters, karst mountain landslide and soil and water loss.

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Computer aided slope stability monitoring

Dorthi Kumar* and Ram Chandar K.

Slope stability accidents are one of the leading causes of fatalities at surface mining operations. Monitoring of the slopes of surface mines can prevent loss of life, destruction of equipment, loss of ore reserves and closure of the mine. In this paper, an attempt is made to review the recent developments in slope stability monitoring system. Zigbee based Wireless Sensor Networks (WSNs) of short distance, low- complexity, low power consumption, low data rate, low-cost, two-way and wireless communication solution for slope stability monitoring system is discussed. A comparison of slope monitoring systems has been done by considering different parameters such as accuracy, update rate, range, slope coverage, weather conditions etc.

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