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Spurt
of Geosignatures Signifying Possible Precursors to a Major
Earthquake in Southwestern Indian Peninsula
- -H
N Singh, D Shanker,
V N Neelakandan, J Mathai, V P Singh and
M Banerjee
Several
clusters of unusual natural incidents have been observed throughout
the Kerala State, Southwestern parts of India during the periods:
February to March, 2001 (phase I), and June to November, 2001
(phase II). The incidences like fluctuations and rise in water
levels, wavy formations and spouting of water in the open
wells, cracks in the buildings, perceptible fissures in the
ground, shaking of trees/bushes and enhanced minor earthquakes
activity have been observed during Phase I; whereas the collapse
of shallow open wells, draining of water, lowering of water
level, land subsidence, ground fissures and further increased
minor earthquake activities, etc., were the dominating incidents
during Phase II. The frequency of occurrences of these incidents
was drastically reduced after November 2001 though. There
are events of a few minor earthquakes which occurred during
2002-2006. The temporal patterns of occurrences of such incidences
during Phase I and Phase II might have been the outcome of
periodic stress release in the region. In the present paper,
the study on the occurrence of the chain of events coupled
with the existence of anomalous seismic activity has been
done in the light of the dilatancy diffusion model and the
results signify that the region is preparing for a major earthquake
in future.
©
2008 IUP . All Rights Reserved.
Estimation
of the Stress Level in the Focal Region Before and After the
December 26, 2004 M9.0 Sumatra Earthquake
- - Chen
Xuezhong
A
method of estimation of the stress level in the focal region
of an earthquake is proposed in this paper. The stress level
in the focal region before and after the December 26, 2004
M9.0 Sumatra earthquake is estimated. The result shows that
the stress value before this major earthquake occurred was
about 2.79 MPa and dropped to 1.51 MPa after its occurrence
with a decrease of about 46%. Therefore, this large earthquake
occurred under a relatively lower stress level.
©
2008 IUP . All Rights Reserved.
Petrophysical
Evaluation of the Lower Cretaceous Thamama III, Northern Offshore
in Abu Dhabi, UAE
- -Amir
Gabr
The
Lower Cretaceous Thamama Group in Zakum oil field is the main
reservoir of the northern offshore oil fields of Abu Dhabi,
United Arab Emirates. This group consists of four formations
in stratigraphic order as: Habshan, Lekhwair, Kharaib and
Shuaiba, and the reservoir facies are developed in parts of
Lekhwair Formation and lower sequence of Kharaib Formation.
In this study, the reservoir quality of Thamama III is evaluated
through vertical and horizontal distribution of the different
petrophysical parameters such as pay zone thickness, shale
content, porosity, permeability, fluid resistivity, water
saturation and hydrocarbon saturation in the zones of interest
for three available logged wells. The study revealed that
the most effective diagenetic events are characterized by
intra-matrix dissolution, moldic porosity and fracturing.
These diagenetic events are followed locally by precipitation
of well-crystalline rhombic dolomite partial cavity and fracture
fillings. The study also documented the observed porosities
ranging between 5% and 31.5%, and permeabilities from less
than 1 to 100 md across the study area and the best reservoir
characteristics are recorded towards northeastern direction,
where the water saturation decreases and the porosity increases.
©
2008 IUP . All Rights Reserved.
Geotechnical
Condition of Subsurface Fluvial Sediments in Pabna Town and
its Adjoining Areas, Bangladesh
- -Md.
Sultan-Ul-Islam, Md. Shamsuzzaman and Md. Badrul Islam
The
town of Pabna covers the northern floodplain of the river
Padma, characterized by abundance of low-lying depressions
and remarkably variable subsurface lithology, which in turn
influences the geotechnical condition. The northern and eastern
parts are characterized by low SPT strength, which is not
suitable for heavy construction. Based on the study of geological
and geomorphological maps, engineering properties of soil,
such as lithology, atterberg limit, consistency, bearing capacity,
plasticity, compaction, consolidation and compressibility,
SPT etc., a geotechnical map is prepared. The study area is
divided into four major unit areas. Unit I is not suitable
at all whereas, unit II is less suitable for heavy construction.
But normal foundation up to the depth of 10 to 18 m below
the surface is needed for the construction of high-rise buildings.
Sediments of unit II are weakly compacted and have medium
plasticity and compressibility. Plasticity of sandy silt and
silty clay is low to medium with high activity. Unit III is
the most suitable for heavy construction with normal foundation
depth up to 3 to 10 m below the surface. It constitutes mainly
sand with low plasticity and low to very low compressibility.
The SPT values vary from 10 to 40. The geotechnical assessment
of the subsurface sediments of the area is essential before
constructing civil engineering structures.
©
2008 IUP . All Rights Reserved.
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