Comparative Evaluations of the Seismic Key Parameter by Artificial Neural Network Model and Ambient Vibration Survey

Kerh Tienfuan1*, Ku Tienchi1 and Gunaratnam David2

Based on a series of historical seismic records, a new weight-based neural network model was developed in this study to estimate peak ground acceleration at a total of 33 train stations in the Kaohsiung mass rapid transit system of Taiwan. The performance of this model was compared with a simple distribution model and an available ambient vibration survey. The comparison of results showed that the neural network models exhibit a variation tendency similar to the microtremor measurements for all the train stations. The results also showed that over 90% of estimations by the weight-based neural network model were smaller than that of the simple distribution model and the former model proved to perform better, as the estimations were closer to the survey data for most of the cases. This type of weight based neural network model might capture the actual response at a construction site more closely and the results obtained confirm that all train stations comply with the seismic requirement of the building code.

Full Text

Earthquake Related Deformation Cycle: Perspectives from 2004 Sumatra and 2010 Chile Mega-Earthquakes

Reddy C.D.1, Arora S.K., 2* Sunil P.S.1 and Prajapati S.K.1

An earthquake cycle consists of pre-seismic, inter-seismic, co-seismic and post-seismic phases of deformation. Studying these processes using geodetic observations facilitates estimating earthquake recurrence time interval. The advances made in space-borne technologies e.g. Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) have made most profound impact on these measurements and understanding of the processes in earthquake cycle. In the past two decades, high resolution observations before, during and after large earthquakes reaffirmed the basic concept of earthquake cycle. The mega earthquakes: Mw 9.3 Sumatra earthquake on December 26, 2004 and the recent Mw 8.8 Chile earthquake on February 27, 2010 and many other such large earthquakes, prompted lithosphere-scale studies in which spaceborne geodetic data are acquired and used to infer the mechanical properties of faults and the rheology of the lower crust and lithospheric mantle. As these parameters essentially control the temporal and spatial distribution of surface strain at all scales, evaluating their characteristics is one of the presentday challenges in continental dynamics. This paper focuses on geodetic, geologic and historic studies, as well as laboratory investigations of the earthquake related deformation cycle.

Full Text

Study on the strong signals of the large floods along the Yangtze River in China

Feng Li Hua

This paper discusses the 3 strong signals for the 3 large floods along the Yangtze River of China since 1900, which are: (1) Sunspot activity, (2) the El Nino phenomenon, (3) Strong earthquakes in the south of the Qinghai-Tibetan Plateau. Their impacts on the abnormal atmosphere circumfluence are referred to as sun-air interaction, ocean-air interaction and land-air interactions respectively. Based on the facts of the large floods along the Yangtze River and the 3 strong signals, the paper discusses the statistic principle of large floods along the Yangtze River and points out that a large flood might occur when the 3 strong signals appear simultaneously and the magnitude of the flood will be even larger when other signals appear. It will help the long-term forecast of large floods along the Yangtze River.

Full Text

Landslide Hazard and Risk Analysis in India at a Regional Scale

Adhikari Manik Das , Nath Sankar Kumar* and Maiti Soumya Kanti

India has about 25% of its geographical area in the mountainous terrain exposing it to wide spread landslides triggered by mainly earthquakes and rainfall. The methodology for Landslide Hazard Zonation (LHZ) and Risk Analysis in India has been carried out in the present study by integrating various thematic layers namely Engineering Geology, Geotectonic (faults/ lineaments), Slope, Geomorphology, Landuse/ Landcover and Rainfall on Geographical Information System and the evolved vector layers subsequently correlated with the existing landslide inventory data. A numerical rating scheme for both the themes and the attributes of each theme has been developed using Information Value Based Method for detailed spatial data analysis. The hazard index map is validated by correlating the landslide frequencies of different classes and a LHZ map is prepared exhibiting four zones, namely “unlikely/low hazard”, “moderate to low hazard”, “high to severe hazard” and “severe to very high hazard”. The risk assessment performed by integrating LHZ with the elements of vulnerability namely population density, road network and landuse /landcover depict that high population density regions are exposed to very high and high landslide hazard activities.

Full Text

High-resolution Seismic Imaging of Geologic Deformation, offshore East Coast of Korea at 37 oN: Implications for Assessments of Seismic Activity

Kim Han-Joon 1*, Jou Hyeong-Tae 1, Lee Gwang Hoon 2, Choi Dong-Lim 1, Yi Bo-Yeon 2, Yoo Lee-Sun 1, Lee Sang-Hoon 1, Kim Kwang-Hee 1 and Yoo Hai-Soo 1

We acquired and interpreted more than 650 km of high-resolution seismic reflection profiles in the Hupo Basin, offshore east coast of Korea at 37 oN in the East Sea (Japan Sea) to image shallow and basement deformation. The seismic profiles reveal that the main depocenter of the Hupo Basin in the study area is bounded by a large offset border fault, the Hupo Fault, on the east and an antithetic fault; however, the antithetic fault is much smaller both in horizontal extension and in vertical displacement than the Hupo Fault. Sediment infill in the Hupo Basin consists of syn-rift (late Oligocene – early Miocene) and post-rift (middle Miocene - Holocene) units. The Hupo Fault and other rift-bounding faults newly defined in the Hupo Basin strike dominantly north. These faults are interpreted to have been created with a sense of normal displacement during continental rifting in late Oligocene to early Miocene times. The current ENE direction of maximum principal compressive stress observed in and around the Korean peninsula associated with the motion of the Amurian Plate induces the faults in the Hupo Basin to have reverse and right-lateral, strike-slip motion, when reactivated. A recent earthquake positioned on the Hupo Fault indicates that in the study area and possibly further in the eastern Korean margin, earthquakes would occur on the faults created during continental rifting in the Tertiary

Full Text

Probability of Occurrence and Study of Earthquake Recurrence Models for Gujarat State in India

Choudhury Deepankar* and Shukla Jaykumar

The probabilistic approach and number of statistical distributions have been adopted by various researchers for computation of seismic risk in terms of conditional probabilities of future earthquakes and earthquake recurrence rates. Using the earthquake catalogue prepared by Institute of Seismological research – Gandhinagar, Gutenberg-Richter (G-R) parameters are then estimated to quantify seismic risk for three seismictectonically different regions i.e. Saurashtra, Kachchh and Mainland Gujarat. Based on the G-R parameter estimated, seismic risk in terms of probability of earthquake occurrence and earthquake return periods are estimated for the three regions of Gujarat. Further, to study earthquake recurrence in Gujarat state, four typical probability density models viz. Exponential, Rayleigh, Pareto and Weibull, have been studied to describe earthquake recurrence time to estimate the next large earthquakes in Gujarat state of India. Time intervals for the occurrence of the next large earthquake in the three region of Gujarat state have been estimated by maximization of conditional probability of earthquake occurrence. Specified four typical probability density models have been checked for its validity for Gujarat based on the last five earthquake event reported. The time interval between the earthquake events have been predicted and compared with observed time for its validation. It is observed that Kachchh region is governing the seismicity in Gujarat state and has high seismic risk compared to other two regions. Comparing the estimated earthquake recurrence interval with the observed data for the last five earthquakes, it is observed that Exponential and Weibull models are appropriate for Gujarat region. Rayleigh Model observed to be giving overestimated recurrence time whereas Pareto Model gives very small recurrence time interval for the Gujarat region.

Full Text

GIS Compatible Software for finding numbers of Topographical and Open Series Maps

Chaure Shailesh Kumar

Topographical maps are indispensable tools for geologists, geographers, foresters, civil engineers, military personnel etc. The process of finding the sheet numbers for irregular polygons like district boarders, watershed boundaries etc. is bit tedious and cumbersome. With the launching of websites like Google Earth and ISRO Bhuvan, finding the latitudes and longitudes of the points and areas of interest has become very easy. Further geo-referenced data in popular GIS software formats are also available from other sources. Recently Survey of India has brought out Open Series Maps (OSMs) on WGS-84 Datum, which have slightly different numbering system than that of the Topographical maps on Everest Datum. Keeping this in mind, an interactive computer programme has been developed for quick and accurate calculation of number of both Topographical Maps and OSMs published by Survey of India. The data input and output are compatible with popular GIS file formats like shape and KML.

Full Text