Term paper on Engineering Seismology, Ground Acceleration and Application of Engineering Seismology

1. Assignment:
Term paper on Engineering Seismology,
Ground Acceleration and
Application of Engineering Seismology
Submitted to:
Sir Faisal Rehman
Submitted by:
Salah Ud Din Shabab
Roll #:
PGLF17E003
Department of Earth Sciences University Of Sargodha,
Sargodha

2. Engineering Seismology:
Engineering seismology lays the bases for calculating seismic hazard, and
includes producing catalogues of historical and instrumental earthquakes, reliable
ground motion mitigation models and high-definition geological underground
models and interpreting historical accounts. Engineering seismologists produce
local seismic hazard maps (micro zonation) and link the results to data on building
vulnerability so that dependable risk assessments can be carried out.
Origins:
Whereas the focus in the past was on what to do after a catastrophic
earthquake, nowadays attention is shifting more and more to prevention,
comprising the implementation of measures designed to mitigate risks. To this
end, engineering seismology aims to lay down and develop corresponding
foundations and methods used to enable the assessment of site-specific seismic
hazards. It combines the disciplines of historical seismology, strong motion
seismology and location effects, numerical modelling and earthquake-induced
phenomena, and then crystallizes that knowledge into basic practical guidelines
for civil engineering, spatial planning and setting technical standards for
construction.
Earthquake Catalogues and Seismic Observations:
A robust earthquake catalogue provides a basis for making statistical
statements about the probability of earthquakes occurring in a certain area.
Historical details of the locations and strength of earthquakes are derived
primarily from observations of their impact on nature, people and buildings. The
consequences are described along with tremor's macroseismic intensity, the
distribution of which serves to calculate the magnitude of historical earthquakes.
Since having a comprehensive earthquake catalogue based on homogeneous
magnitudes is an essential prerequisite for forecasting seismic hazards, gathering
macroseismic intensity data is also an important task in the modern era of
instrumental recording, because it helps us improve the calibration of historical
quakes in the future.
Microzonation – Looking into the Local Geological
Underground:
Compared with solid, rocky ground, soft soils like valley floors, riverbanks
and lake shores can amplify seismic tremors by a factor of up to 10 (in extreme
cases). Consequently, in addition to producing seismic hazard maps showing

3. regional differences in risk levels, the likelihood of site-specific underground
tremors also has to be ascertained, in so-called microzonation studies. These
studies entail the geological and geotechnical mapping of unconsolidated
sediments, the analysis of slope stability and the potential for soil liquefaction,
the use of geophysical measurements to predict amplifications of seismic waves,
and numerical simulations calibrated to earthquake recordings.
Risk Analysis – an Instrument for Planning Earthquake
Mitigation:
A medium earthquake risk combined with a dense population and high
value concentration means that highly populated areas faces a high seismic
hazard. The quantification of the actual risk level is based on maximally realistic
earthquake damage scenarios. Building vulnerability is also taken into account in
so-called 'fragility curves' and combined with expectations about local seisms.
Scenarios like this enable forecasts to be made about the potential physical and
financial damage and numbers of fatalities, injuries and homeless people in the
wake of an earthquake. Another key point entails the accurate factoring in of
uncertainties when calculating damage scenarios. At the time of writing, all
school buildings in the canton of Basel were being analysed using such a risk
model, focussing in particular on issues associated with the cost-effectiveness of
seismic retrofitting measures.
Ground Acceleration:
During an earthquake when the ground is shaking, it also experiences
acceleration. The peak acceleration is the largest increase in velocity recorded by
a particular station during an earthquake.
Seismic ground acceleration (force per unit of mass) plays an
important role in assessing effects of earthquakes on the built
environment, persons, and the natural environment. It is a basic parameter of
seismic wave motion on which earthquake resistant building design and
construction are based. Thelevel of damage is, among other factors, directly
proportional to the severity of the ground acceleration, and it is important
information for disaster-risk prevention and mitigation programs.
Knowledge of the spatial distribution of maximum seismic acceleration in
an urban area, due to strong-earthquake shaking, is important for territorial
planning and use, urban development, risk management, implementation of
disaster prevention measures, community emergency prepare dness and other
applications. This knowledge is developed through seismic microzoning of urban

4. areas for reliable strong motion estimation, either through comprehensive
geophysical geotechnical surveys and appropriate enumerical modeling, or from
having as many seismic strong-motion instruments as possible recording a strong
and destructive earthquake.
In both cases, significant financing and a long time waiting for an event to
occur are required. However, if a destructive earthquake strikes an urban area,an
approximate ground response can be attained through systematic observations of
macroseismic effect sand a careful ground shaking severity rating, when no such
strong motion seismic network exists. In this paper, we report this kind of
experiment and the use of macroseismic, geotechnical and
predominant frequency data to quantitatively estimate maximum ground
acceleration.
Peak ground acceleration:
(PGA) is equal to the maximum ground acceleration that occurred during
earthquake shaking at a location. PGA is equal to the amplitude of the largest
absolute acceleration recorded on an accelerogram at a site during a particular
earthquake. Earthquake shaking generally occurs in all three directions.
Therefore, PGA is often split into the horizontal and vertical components.
Horizontal PGAs are generally larger than those in the vertical direction but this
is not always true, especially close to large earthquakes. PGA is an important
parameter (also known as an intensity measure) for earthquake engineering, The
design basis earthquake ground motion (DBEGM) is often defined in terms of
PGA.
Unlike the Richter and moment magnitude scales, it is not a measure of the
total energy (magnitude, or size) of an earthquake, but rather of how hard the
earth shakes at a given geographic point. The Mercalli intensity scale uses
personal reports and observations to measure earthquake intensity but PGA is
measured by instruments, such as accelerographs. It can be correlated to
macroseismic intensities on the Mercalli scale but these correlations are
associated with large uncertainty.
The peak horizontal acceleration (PHA) is the most commonly used type
of ground acceleration in engineering applications. It is often used within
earthquake engineering (including seismic building codes) and it is commonly
plotted on seismic hazard maps.[5] In an earthquake, damage to buildings and
infrastructure is related more closely to ground motion, of which PGA is a
measure, rather than the magnitude of the earthquake itself. For moderate
earthquakes, PGA is a reasonably good determinant of damage; in severe
earthquakes, damage is more often correlated with peak ground velocity.

5. Application of Engineering Seismology:
The scope of engineering seismology includes geotechnical site
investigations for buildings and engineering infrastructures, such as dams, levees,
bridges, and tunnels, landslide and active- fault investigations, seismic
microzonation, and geophysical investigations of historic buildings. These
projects require multidisciplinary participation by the geologist, geophysicist, and
geotechnical and earthquake engineers. The broader scope of engineering
seismology also includes exploration of earth resources, including groundwater
exploration, coal and mineral exploration, and geothermal exploration. While
focusing on the application of the seismic method to geotechnical site
investigations, this book includes many case studies in all of the applications of
engineering seismology.
Engineering seismology is the study and application of seismology for
engineering purposes. It generally applied to the branch of seismology that deals
with the assessment of the seismic hazard of a site or region for the purposes of
earthquake engineering. It is, therefore, a link between earth science and civil
engineering.
There are two principal components of engineering seismology. Firstly,
studying earthquake history (e.g. historical and instrumental catalogs of
seismicity) and tectonics to assess the earthquakes that could occur in a region
and their characteristics and frequency of occurrence. Secondly, studying strong
ground motions generated by earthquakes to assess the expected shaking from
future earthquakes with similar characteristics. These strong ground motions
could either be observations from accelerometers or seismometers or those
simulated by computers using various techniques, which are then often used to
develop ground motion prediction equations.
References:
Allaby, Ailsa; Allaby, Michael, eds. (2003). Oxford Dictionary of Earth Sciences (Second
ed.). Oxford University Press.
Ben-Menahem, Ari (1995), "A Concise History of Mainstream Seismology: Origins, Legacy,
and Perspectives" (PDF), Bulletin of the Seismological Society of America, Seismological
Society of America, 85 (4): 1202–1225
Ewing, W. M.; Jardetzky, W. S.; Press, F. (1957). Elastic Waves in Layered Media. McGraw-
Hill Book Company.
Gubbins, David (1990). Seismology and Plate Tectonics. Cambridge University Press. ISBN
0-521-37141-4.

6. Hall, Stephen S. (2011). "Scientists on trial: At fault?". Nature. 477 (7364): 264–269.
Bibcode:2011Natur.477..264H. doi:10.1038/477264a. PMID 21921895.
Kanamori, Hiroo (2003). Earthquake prediction: An overview (PDF). International Handbook
of Earthquake and Engineering Seismology. 81B. International Association of Seismology &
Physics of the Earth's Interior. pp. 1205–1216.
Lay, Thorne, ed. (2009). Seismological Grand Challenges in Understanding Earth's Dynamic
Systems (PDF). Report to the National Science Foundation, IRIS consortium.
Schulte, Peter; Laia Alegret; Ignacio Arenillas; José A. Arz; Penny J. Barton; Paul R. Bown;
Timothy J. Bralower; Gail L. Christeson; Philippe Claeys; Charles S. Cockell; Gareth S.
Collins; Alexander Deutsch; Tamara J. Goldin; Kazuhisa Goto; José M. Grajales-Nishimura;
Richard A. F. Grieve; Sean P. S. Gulick; Kirk R. Johnson; Wolfgang Kiessling; Christian
Koeberl; David A. Kring; Kenneth G. MacLeod; Takafumi Matsui; Jay Melosh; Alessandro
Montanari; Joanna V. Morgan; Clive R. Neal; Douglas J. Nichols; Richard D. Norris;
Elisabetta Pierazzo; Greg Ravizza; Mario Rebolledo-Vieyra; Wolf Uwe Reimold; Eric Robin;
Tobias Salge; Robert P. Speijer; Arthur R. Sweet; Jaime Urrutia-Fucugauchi; Vivi Vajda;
Michael T. Whalen; Pi S. Willumsen (5 March 2010). "The Chicxulub Asteroid Impact and
Mass Extinction at the Cretaceous-Paleogene Boundary". Science. AAAS. 327 (5970): 1214–
1218. Bibcode:2010Sci...327.1214S. doi:10.1126/science.1177265. ISSN 1095-9203. PMID
20203042. Retrieved 5 March 2010.
Shearer, Peter M. (2009). Introduction to Seismology (Second ed.). Cambridge University
Press. ISBN 978-0-521-70842-5.
Stein, Seth; Wysession, Michael (2002). An Introduction to Seismology, Earthquakes and
Earth Structure. Wiley-Blackwell. ISBN 978-0-86542-078-6.
Wen, Lianxing; Helmberger, Donald V. (1998). "Ultra-Low Velocity Zones Near the Core-
Mantle Boundary from Broadband PKP Precursors" (PDF). Science. 279 (5357): 1701–1703.
Bibcode:1998Sci...279.1701W. doi:10.1126/science.279.5357.1701