Ramesh
P. Singh [Saturday, January 26, 2002 8:56 AM]
hello,
What
I believe that for seismic codes of any country, the most crucial input
is the seismic zoning map. The way we have prepared the seismic zoning
map of India is NOT AT ALL correct and whatever the seismic codes exist
or developed are not correct. The important contributions of the scientists
and engineers of India, is to make coordinated efforts to make a reliable
seismic zoning map of India before we discuss Sesismic codes, I am afraid
that unless we do this all other efforts are in vain. I would like
to know the thinking of my colleagues and friends.
Ramesh
P. Singh
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S.P.
Badami [Saturday, January 26, 2002 5:42 PM]
Reply
to Prof. Ramesh P Singh, IITK:
"........ before we discuss Seismic codes, I am afraid that unless
we do this all other efforts are in vain....."
Knowledge and understanding of earthquakes and behavior of structures
keeps improving over a period of time. The main objective is providing
safe economic structures. We know that higher the self weight of a structure,
greater is the stability against wind. We also know that it is quite opposite
where earthquake is concerned. It is also folly not to remember that the
stiffness and mass govern the behavior of the structure to earthquakes.
It may be of academic interest to first have the Seismic Zone Map of India
corrected and then discuss seismic codes. Then it might as well be that
we do not construct buildings because we still need to do the basics!
There were certain anomalies in the IS:1893-1984 which not only are needed
to be discussed by us but addressed to in the Draft Code. The geologists
and concerned seismologists/engineers might work on correcting the Zoning
Map of India. If we keep waiting for this then the draft seismic code
we will perhaps see the light of day in 2010? Actually the system should
be such that these important codes should get revised every three years,
with the process commencing from the day the draft code comes into being.
We have a strong track record of stability:
IS:456-2000 was revised after 22 years
IS:800-1984 yet to be revised after 18 years
IS:1893-1984 the draft code is due to come out any time - 18 Years later
IS:4326-1976 revised to IS:13920-1993 took 17 years and now already 9
years old.
IS:875-1987 was revised after 23 years and is already 15 years old
Is there anything more to say on this?
Sudhir Badami
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Ramesh
P. Singh [Saturday, January 26, 2002 8:20 PM]
hello
Mr. Sudhir Badami,
Thanks for your response. I am surprised to read
"It may be of academic interest to first have the Seismic Zone Map
of India corrected and then discuss seismic codes. Then it might
as well be that we do not construct buildings because we still need
to do the basics!
This is the problem with us. We do not think anything in totality. We
always try to think within the domain in which we are interested, taking
other things granted. We should also think seriously the main basis for
the change of codes or upgradation of codes. Saying that Seismic zoning
map and its upgradation is of academic interest, has really surprised
me. In such case, I can also say that upgradation of seismic codes is
also of academic interest when we know that what type of buildings are
being made in most vulnerable seismic prone regions/countries like Japan
and in California. What I see that Seismologists, Geologists, Geophysicists
and Engineers are trying to work in their individual domain, and
this leads us to think that draft seismic code will perhaps see
the light of day in 2010? If we make coordinated efforts, I have
no doubts that we can see the draft within no time. Otherwise, we will
delay any project like the good example of Tehri is before all of us.
R.P. Singh
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Arzhang
Alimoradi [Sunday, January 27, 2002 1:09 AM]
Response
to Mr. Sudhir Badami
I have to say that I agree with Professor Singh. As you might be aware,
this field of science/practice is already a multidisciplinary one. There
is not much difference between our academic issues (in different fields)
and those we face in real life or in industry. Input from different fields
is necessary. Lack of precise Seismic Hazard Maps shall not prevent us
or distract our attention form considering the basics (and I do really
mean basics) of the seismic design, in which the structure would behave
relatively acceptable during a seismic event which in turn will save lots
of lives. I would like also to add one more thing: Seems to me that most
of the discussions here are focused on Building Codes, which are naturally
important. But, isn't that important too, to be concerned about
the art of seismic design which is independent of any specific code? The
rules of the nature do not obey any national code! A successful
designer is one who understands/feels/pictures these rules and so his
artwork behaves in a way the designer had wanted to. It's obvious though
it's where we are heading now. "Performance Based Seismic Engineering".
Prescriptive Design Codes have shown enough their capabilities. "Consequence
Based Engineering" proposed recently at MAE center is another approach
that might be of interest too. Overall, very interesting discussions.
Thanks to the organizers and participants.
Arzhang Alimoradi
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Jitendra
K. Bothara [Sunday, January 27, 2002 9:18 AM]
Hi
Colleagues,
It is interesting to join you all on this issues. I have few remarks (?)
on lapping of bars, seismic zoning map and other issues. These are:
….
2.
Seismic Zoning map
I agree with prof. Singh that we must see every thing in totality but
I think issue of seismic zoning map should not hinder up coming process.
I think, from procedural aspect, seismic code can be divided in two major
parts: a) seismic zoning map which is more multidisciplinary in nature
and of course discussion should be on it as well. And next is b) design
loads/ design approach which is more engineering in nature. Regarding,
seismic zoning map, it do not match in boundary region of US and
Canada even though both are prepared very rationally. Even seismic zoning
map of Nepal (NBC105-1994, draft) very much differs with IS1893-1985 (sorry
I donot have IS1893-2001). Nepal seismic zoning map considers higher seismicity
in central-west Nepal and gradually reducing in north and south. It considers
a seismic gap roughly between west of Kathmandu and Dehradun alomg middle
mountains. There are people who do not ready to reconize any such seismic
gap. Similarly, a lot of conflict exists in intraplate earthquakes, its
strength etc. Any seismic zoning map prepared considering or omitting
seismic gap or taking consideration of other conflicts would be quite
different. Again, it is not only seismic force that affects the damagability
of a building, it is more a building itself. A well designed, detailed
and well constructed building should be ideally insensitive to force level
as it would go in inelastic regime in severe earthquake.
…..
It
is all for now. See you later.
Jitendra K. Bothara
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S.P.
Badami [Sunday, January 27, 2002 11:46 AM]
Response
to Dr R P Singh and Arzhang Alimoradi,
I
mean that Seismologists and Geologists may find it of academic interest
to upgrade the Seismic Zoning Map of India, hence may proceed with speed
lower than needed as their resources may not be adequate to carryout the
needed research. But the buildings have to be built with the state of
the knowledge of earthquakes and structure's responses to them. The normal
professional engineer cannot be expected to do this task of correcting
Seismic Zoning Map, hence it is left to the Code's Committee to upgrade
the codes keeping in view the quality of information available and needed
and the speed with which it is needed.
Until
more precise data is available, we have to make do with what is available
and do so intelligently. Which some lacunae existing in the seismic codes,
or wrong understanding of some clauses, it is necessary to get a better
understanding and that is easily possible through an e-conference like
this.
When
I say 'of academic interest', I mean that the time frame is of little
consequence and hence resources deployed are also meager, which results
in getting things progressing at slow pace. If catastrophes set the pace
for development of the correct Seismic Zoning Map then we have had Latur
and Bhuj to remind us. Discussions on seismic codes itself may put pressure
on appropriate authority to take initiative in making that happen. Lot
of things have to go on simultaneously unless there is a danger of gross
contradiction.
Upgrading
Seismic Codes is not an exercise of academic interest alone. The lacunae
and anomalies in the existing codes have to be addressed with the additional
knowledge and understanding of the subject since their last publication
in 1984. It is a document to be used extensively by Structural Engineers.
More
on the lacunae and anomalies separately.
Sudhir
P Badami
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Ramesh
P. Singh [Sunday, January 27, 2002 12:33 PM]
Dear
Mr. Sudhir Badami,
Discussions on seismic codes itself may
> put pressure on appropriate authority to take initiative in making
that happen. Lot of things have to go on simultaneously >unless
there is a danger of gross contradiction.
My main contention is that one should not talk about the seismic codes
without accounting sesimic zoning maps. The Earthquake Engineers of this
country have never bothered about the seismic zoning map, they are only
bothering about the seismic codes. If they start bothering, they can force
the Government/agencies to upgrade sesmic zoning map which is one of the
crucial input to the Sesimic codes.
R.P. Singh
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M.
Hariharan [Sunday, January 27, 2002 21:52 PM]
Arzhang
Alimoradi wrote:
>
..... "Consequence Based Engineering"
> proposed recently at MAE center is another approach that might be
of interest too.
> Overall, very interesting discussions. Thanks to the organizers and
participants.
Arzhang,
The
idea of consequence based engineering, from the title, looks appealing.
Could you elaborate the concept please?
Hariharan
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Shashikant
N Sarada [Sunday, January 27, 2002 23:45 PM]
>
Arzhang,
> The idea of consequence based engineering, from the title, looks
appealing. Could you elaborate the concept please?
> Hariharan
Targeting
new loss reduction measures through a unified approach is known as Consequence-Based
Engineering (CBE), this term has been coined by Mid-America Earthquke
(MEA) Center. The process of Consequence-Based Engineering is cyclical,
with consequence assessment followed by an intervention method for consequence
minimization, then re-assessment after intervention, leading to the achievement
of an acceptable set of consequences on the economic and social levels.
Following
are the objectives of MAE Center Education Program and are relevant to
this e-conference.
1
Promote student involvement in research through symposia, student groups,
field missions, internships, and relevant research experiences.
2 Advance undergraduate and graduate engineering curricula with new cross-
disciplinary programs in earthquake engineering.
3 Develop tools to enhance learning of earthquake engineering at the undergraduate
and graduate levels.
4 Outreach to pre-college students.
5 Enhance public awareness and transfer advanced earthquake engineering
knowledge and technology to engineering practitioners.
For more information on CBE visit mae.ce.uiuc.edu/Research/BodyNV.htm
Regards,
-Shashikant
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Arzhang
Alimoradi [Monday, January 28, 2002 1:17 AM]
Thanks
for your comments.
All I say is that: It's generally possible for an earthquake engineer
to design a building to survive an earthquake having little or even not
accurate information about the level of seismic hazard in the region.
I want even to go one more step further: It's also doable without having
access to the sophisticated computational tools! We have plenty
of examples around.
Policy making, refining the maps, advanced analysis techniques such as
Time history analysis, Push-over, yield point spectra, advanced technologies
such as base isolation, active/passive/hybrid methods are all interesting
and promising. Though what we ignore most of the times is basics of earthquake
resistant design: soft story problems, irregularities in height and plan,
uniform distribution of mass and lateral load bearing elements throughout
the structure, ductility, torsion, ... Otherwise static method (seismic
coefficient) is generally more than enough for most of the simple structures.
No need even for more refined analyses.
Thanks again.
Arzhang Alimoradi
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Arzhang
Alimoradi [Monday, January 28, 2002 2:01 AM]
Dear
All and Dear Hariharan;
First
I appreciate Shashikant 's quick answer to Hariharan 's question, though
a big part of that reply was basically related to the MAE center education
program and not very much related to CBE as one of the major projects
of the center. I would invite you to please refer to the descriptions
of projects FD-1 to FD-3 on MAE center web site at: http://mae.ce.uiuc.edu/Research/EP.htm
To
put it in simple words: we have now three major approaches under development
(some already in implementation phase): 1. Performance Based Design: as
the new generation of seismic codes vs. traditional prescriptive
codes: How to design the structures in order to perform in a way we (designers/owners)
want, during a seismic event.
2. Consequence Based Engineering: It's mostly a system based approach:
How to design a system of infrastructures (or to retrofit) to minimize
the consequences of a disaster. It's especially attractive for such regions
like Mid Amercia where intraplate earthquakes happen not too frequently
but strong enough to affect a big region (because of the attenuation characteristics
of the central and eastern United States, they can be really damaging)
Again: System Based: So it's an study over a system of, for an example,
infrastructures, networks,...
3. New technologies: active structural control, passive energy dissipation,
hybrid control, based isolation techniques, structural health monitoring,...
Question: Is anybody aware of any applications of base isolation techniques
in India? There are a few simple/effective/and cheap methods that
can be implemented easily. One was proposed in Iran a few years ago where
you can put One/Two story residential buildings over a thin layer of sand
spread over a raft foundation, as a friction type isolation system. I
appreciate any inputs in this matter. I hope this could help. You can
also find plenty of information on these topics on Internet.
Best
Regards;
Arzhang
Alimoradi
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Jitendra
K. Bothara [Monday, January 28, 2002 3:04 AM]
It
is intresting to participate the discussion on seismic zoning map. I fully
agree with Mr. Alimoradi's comment on seismic zoning. Of course seismic
zoning map is first step of earthquake resistant design but more important
is basics of earthquake resistant design and construction whcich are lagging
most of the time. With a good undersatanding of building behavior, a earthquake
resistant building can be designed even without very accurate seismic
map or sophisticated computational tools. Of course, a blunder in seismic
zoning map could be fatal. I am not trying to undermine worth of seismic
zoning map.Its improveement with development in earth science is important
as well. I understand, one hospital is under construction with base-isolation
in Bhuj with NZ technical assistance.
Jitendra K bOthara
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C.V.R.
Murty [Wednesday, January 30, 2002 2:00 PM]
Seismic
Zone Maps
============
A lot has been said on the seismic zone maps so far. I am particularly
thankful to Dr. Ramesh P.Singh, Professor of Geophysics at IIT Kanpur,
for kicking off the discussion on such a vital topic. I realise that the
topic is too vast and complex. To demonstrate the same, I am penning a
few basic remarks on the complexities involved in the efforts of seismic
zoning. The following is not a description of the process of evolving
a seismic zone map, but it just gives a rough idea of areas where we need
to concentrate. The seismic zones maps can be of different levels of precision.
----------------------------------------------------------------------------
Stage (a)
DATA :: Use isoseismals from past EQs.
PROCESS:: On a map of India, for each place, obtain the maximum intensity
sustained during past EQs. Identify all areas with equal seismic shaking
intensity (on MSK Scale).
Make seismic zones as below
:: Places with Intensity V and less - Zone I
:: Places with Intensity VI - Zone II
:: Places with Intensity VII - Zone III
:: Places with Intensity VIII - Zone IV
:: Places with Intensity IX and more - Zone V
----------------------------------------------------------------------------
Stage (b)
DATA :: As in (a) above plus and existing known ACTIVE faults (with magnitude
M_max of projected size of largest EQ in future on each).
PROCESS 1 :: Relate the M_max on the fault to the intensity at different
distances from it using attenuation relations (M versus Intensity) applicable
for the region. (We need enough data from different parts of India to
have reliable attenuation relations for the different regions of the country.)
Do this with all known active faults. Now continue the seismic zoning
as in stage (a) above.
OR
PROCESS 2 :: Relate the M_max on the fault to the peak ground accelerations
at different distances from it using attenuation relations M versus
accelerations) applicable for the region. (Again, we need enough
data from different parts of India to have reliable attenuation relations
for the different regions of the country.) Do this will all known active
faults.
Make seismic zones as below
:: Places with accelerations 0.0-0.1g - Zone I
:: Places with accelerations 0.1-0.2g - Zone II
:: Places with accelerations 0.2-0.3g - Zone III
:: Places with accelerations 0.3-0.4g - Zone IV
:: Places with accelerations 0.4g and more - Zone V
(The acceleration ranges indicated here are just for discussion purposes.)
PROCESS 2 may be preferred over PROCESS 1.
----------------------------------------------------------------------------
Now, we need to add the data from other complexities::
1. Paleoseismic Studies on Active and Passive Faults - Paleoseimologists
trench across faults and study all past slips and associate a size (Magnitude)
with each of them. That gives a better idea of the largest size of the
EQ that has already taken place along those faults.....
2. Strong ground motion instrumentation data from the neighbourhood of
faults - Strong motion instruments (accelerometers) are placed on ground
along the neighbourhood of faults. And, one may be lucky to have instruments
in the neighbourhood of faults when earthquakes take place on them. The
actual levels of accelerations generated there are captured on them.
3. Near-field (or near-fault) effects in the ground motions - If the instruments
placed are in the near-neighbourhood of the faults, the special spikes
in the strong ground motions very close to faults can be captured.
4. Identifying new faults through detailed geological studies.
5. Probability of occurrences of earthquakes and the magnitudes associated
with them.
6. Many more ...
----------------------------------------------------------------------------
Stage (z)
DATA::
Earthquake source, seismicity and geometry = Fault lines, fault planes,
probability density function for the magnitude of the projected maximum
earthquakes on all points on those faults.
Attenuation curves for peak ground accelerations with distance = the probability
distributions for different magnitudes of earthquakes
PROCESS::
For each value of annual probability of exceedance, obtain the associated
peak ground acceleration value for each location due to the projected
maximum earthquake occurring at each point on the fault line or fault
plane. Make seismic zones with places of acceleration contours with same
annual probability of exceedance. Thus, there will be many maps with different
annual probabilities of exceedance. The above procedure may be repeated
with spectral accelerations instead of peak ground accelerations.
----------------------------------------------------------------------------
Clearly, the involvement of structural and geotechnical engineers,
eologists, geophysicist, seismologists, paleoseismologists, seismotectonicists,....
keeps increasing with each Stage. Also, the extent of probabilistic concepts
also increase with each Stage. We need a critical mass of professionals
with diverse backgrounds mentioned above to be dedicated towards making
the seismic zone map in India, before we can see monumental progress in
the seismic zone maps of the country....
The seismic zone map in the current Indian seismic code (IS1893:1984)is
at Stage (a), and that in the draft code is an attempt towards Stage
(b). In India, seismic zone map making process needs to evolve a long
way to reach the State-of-the-art Seismic Zone Map in Stage (z) or thereabouts
that some countries with advanced seismic provisions are already actively
pursuing.....
c.v.r.murty
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Durgesh
Rai [Wednesday, January 30, 2002 6:26 PM]
More
on zoning maps:
Zoning maps has been the second most discussed topics so far. They are
also the second most item (after the magnitude) to be discussed in the
media after the occurrence of a destructive earthquake! They are very
important as a statement on relative seismic hazard for a given region
not only for general awareness about earthquakes but also for engineering
purposes. The hazard parameter enters into the seismic force calculation
for design of structures, and therefore, they are integral part of the
seismic codes. There have been concerns regarding the philosophy and techniques
that have been used to derive the seismic zone map in IS 1893. Some of
the difficulties arise due to sparse database of past earthquakes (seismicity),
especially in the Deccan area and their effects, known mostly in qualitative
terms from intensity observations. The recent trend worldwide is that
these maps are not only probability based (to go with probabilistics based
design approach) but also expressed in terms of spectral accelerations
and velocities which are closely related to response quantities
of structure (unlike peak ground acceleration or intensity), which are
of interest to engineers. These can be directly used to derive design
spectra for a given site. Further, site soils effects and near source
effects can be included in the design spectrum with relative ease.
Damage based intensity scales such as MSK are based on damage to 'small'
buildings and do not really reflect the behaviour of major engineered
structures such as multi-storeyed buildings (damage to high-rise buildings
in Ahmedabad is a case in point). Our present zoning map draws heavily
from these intensity observations. In this context, I agree with CVR Murty
that a lot more has to be done in the country by way of collecting instrumented
data, improving the quality of available historical data, understanding
various probable sources of earthquakes in a given area, etc. before a
rational zone map along the current thoughts can be developed. It is a
difficult problem indeed, but certainly doable. I would like to hear from
those who are more familiar with the process of developing zone maps for
IS 1893 and what do they think about the probable roadmap for developing
state-of-art of zone maps suggested by CVR Murty. Fortunately, as
past experience has shown (and rightly pointed out by previous discussers)
that a well detailed earthquake-resistant structure is most likely to
survive a collapse even in an earthquake which may cause forces much larger
than those estimated by using current zone maps. I believe this
force-insensitivity of properly detailed structure (adequate deformability
with stability) convinces engineers to pay far greater attention to detailing
aspects than to worry about accurately estimating the earthquake forces!
Nonetheless, it is not to suggest that engineers have ignored or underestimated
the utility of these maps. Better and rational zoning maps are always
helpful in realizing safe and economical structures.
Durgesh Rai
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Ramesh
P. Singh [Thursday, January 31, 2002 2:23 AM]
dear
Dr. Murty,
I read your basic remarks on Seismic zoning with great interest.
Let me start with your concluding comments:
The seismic zone map in the current Indian seismic code (IS1893:1984)
> is at Stage (a), and that in the draft code is an attempt towards
> Stage (b). In India, seismic zone map making process needs to evolve
> a long way to reach the State-of-the-art Seismic Zone Map in Stage
(z)
> or thereabouts that some countries with advanced seismic provisions
> are already actively pursuing.....
I do not know the Stages of Seismic Zone map listed by you, are your
thoughts or you have read somewhere. If it is listed somewhere I would
like to know the reference.
You wrote that the Current Zone map is at stage (b) and we will take long
way to achieve Stage (z) whereas other countries are quite advanced.
Let me go the gross root, why it has happened!! or happening!!
We are all responsible, specially the young scientists/engineers in
general. I do not want to elaborate but you can think!
You will agree with me that seismic zoning map requires a
coordinated effort but what we are doing in this country. Ever since
Koyna the scientists/engineers are competing with each other and as
a result nothing is moving neither the Seismic zoning map nor the Tehri
dam!! The story is still continuing, is there any coordination among
scientists/engineers!!!!! I think all of us should think seriously if
we
have to achieve something is this country.
Let me give my specific comments (read below):
On Wed, 30 Jan 2002, C. V. R. Murty wrote:
> ----------------------------------------------------------------------------
> Stage (a)
> DATA :: Use isoseismals from past EQs.
> PROCESS:: On a map of India, for each place,
> obtain the maximum intensity sustained during past EQs.
> Identify all areas with equal seismic shaking intensity (on MSK Scale).
> Make seismic zones as below
> :: Places with Intensity V and less - Zone I
> :: Places with Intensity VI - Zone II
> :: Places with Intensity VII - Zone III
> :: Places with Intensity VIII - Zone IV
> :: Places with Intensity IX and more - Zone V
RP's --
Well, earthquakes have recurrence cycle of 50 - 100 years. I do not think
that we have very good records of Intensity and moreover not many major
earthquakes have occurred in shield areas. In the Himalayn region, we
have
better record and I can say that in this region, our seismic zoning map
is
around Stage (z) and one can achieve in complete sense if we do
coordinated efforts.
In the shield region, for the intraplate earthquakes, I do not think
one can classify the seismic zones based on isoseismals. For the
intraplate earthquakes (apart from Bhuj) isoseismals are quite different
and their characteristics are also different.
> ----------------------------------------------------------------------------
> Stage (b)
> DATA :: As in (a) above plus
> and existing known ACTIVE faults
> (with magnitude M_max of projected size of largest EQ in future on
each).
>
> PROCESS 1 :: Relate the M_max on the fault to the intensity at
> different distances from it using attenuation relations (M versus
Intensity)
>
> applicable for the region. (We need enough data from different parts
of
> India to have reliable attenuation relations for the different regions
of
> the country.)
> Do this with all known active faults.
> Now continue the seismic zoning as in stage (a) above.
RP's Comment : Let me leave Himalayn region since we are close to Stage
(z). For shield region, we do not have much knowledge and also it is
difficult to know about the faults and more about active faults except
few. In this region, the characteristics of intraplate earthquakes
are entirely different so I do not think most of the time faults are
the source of earthquakes. so the above approach is not feasible.
> OR
>
> PROCESS 2 :: Relate the M_max on the fault to the peak ground
> accelerations at different distances from it using attenuation relations
> (M versus accelerations) applicable for the region. (Again, we need
> enough data from different parts of India to have reliable attenuation
> relations for the different regions of the country.)
> Do this will all known active faults.
> Make seismic zones as below
> :: Places with accelerations 0.0-0.1g - Zone I
> :: Places with accelerations 0.1-0.2g - Zone II
> :: Places with accelerations 0.2-0.3g - Zone III
> :: Places with accelerations 0.3-0.4g - Zone IV
> :: Places with accelerations 0.4g and more - Zone V
> (The acceleration ranges indicated here are just for discussion purposes.)
RP'S comments:
Again, I am ignoring Himalayan region. Since we do not have knowledge
of
faults and so far no guess of attenuation relation, again this approach
is
not feasible.
>
> PROCESS 2 may be preferred over PROCESS 1.
RP's Comments: No question of preference based on above commnets.
> ----------------------------------------------------------------------------
> Now, we need to add the data from other complexities::
>
> 1. Paleoseismic Studies on Active and Passive Faults -
> Paleoseimologists trench across faults and study all past slips and
> associate a size (Magnitude) with each of them. That gives a better
idea of
> the largest size of the EQ that has already taken place along those
> faults.....
RP--
?????
In shield region - it is almost impossible.??????????????????????
> 2. Strong ground motion instrumentation data from the neighbourhood
> of faults -
> Strong motion instruments (accelerometers) are placed on ground along
> the neighbourhood of faults. And, one may be lucky to have instruments
> in the neighbourhood of faults when earthquakes take place on them.
> The actual levels of accelerations generated there are captured on
them.
>
RP--
This way one has to wait may be million years???
> 3. Near-field (or near-fault) effects in the ground motions -
> If the instruments placed are in the near-neighbourhood of the faults,
> the special spikes in the strong ground motions very close to faults
> can be captured.
The intraplate earthquakes are not related to faults, I do not think we
can get enough and sufficient data, again we have to wait million years.
> 4. Identifying new faults through detailed geological studies.
RP----
Impossible to know about new faults using geological studies, one can
get
information from geophysical studies but it is also impossible, most of
the faults are subsurface faults. Some are mapped which are subsurface.
Moreover,. there is not much use by identifying the faults in shield
region.
> 5. Probability of occurrences of earthquakes and the magnitudes
> associated with them.
>
RP-- One can not get anything
6. Many more ...
> ----------------------------------------------------------------------------
> Stage (z)
> DATA::
> Earthquake source, seismicity and geometry =
> Fault lines, fault planes, probability density function for the magnitude
> of the projected maximum earthquakes on all points on those faults.
>
> Attenuation curves for peak ground accelerations with distance =
> the probability distributions for different magnitudes of earthquakes
RP's
One of the important parameters which control the attenuation relation
is
the surface and subsurface geology which is quite variable in Indian
shield.
> PROCESS::
> For each value of annual probability of exceedance,
> obtain the associated peak ground acceleration value for each location
> due to the projected maximum earthquake occurring at each point
> on the fault line or fault plane.
> Make seismic zones with places of acceleration contours
> with same annual probability of exceedance.
> Thus, there will be many maps with different annual probabilities
of
> exceedance.
>
> The above procedure may be repeated with spectral accelerations instead
of
> peak ground accelerations.
RP's ------------
Not feasible at all.
> ----------------------------------------------------------------------------
>
> Clearly, the involvement of structural and geotechnical engineers,
> geologists, geophysicist, seismologists, paleoseismologists,
> seismotectonicists,.... keeps increasing with each Stage.
> Also, the extent of probabilistic concepts also increase with each
Stage.
> We need a critical mass of professionals with diverse backgrounds
> mentioned above to be dedicated towards making the seismic zone map
> in India, before we can see monumental progress in the seismic zone
maps
> of the country....
RP's
I am of the opinion that you divide whole Indian region into three zones.
For the shield region one should see carefully the geology and attenuation
of the seismic waves. For the shield region, one may consider significant
amount of earthquake loads while designing the building rather than
designing on the basis of five zones.
What is important in our country is that we should take a reasonable
earthquake load and design the building honestly. The 75 buildings in
Ahmedabad are the example of our honesty.
Ramesh P. Singh
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Ramesh
P. Singh [Thursday, January 31, 2002 2:46 AM]
Dear Dr. Murty,
One thing I forgot to add, in shield region, one should make efforts
to map the lineaments (fractures/faults) using remote sensing data and
also computes the orientaion of stresses. The deatils of mapping these
fractures/faults and calculations of stresses are given in my papers
(current science and International J. Remote sensing and also reports
submitted to DST). While selecting sites for small or mega projects
specially in shield region, one should try to avoid high lineament density
regions. Unfortunately, we do not have lineament maps of Indian region.
When Koyna earthquake occurred, the Americans did generate lineaments
map
of the region. The generation of lineaments map at smaller scale should
be
used in the microzonation of the shield region which can be used for
guiding the earthquake loads specially in the shield region in the absence
of so many parameters in the shield region. The lineaments are good
representaive of the subsurface or tectonic activities of the shield
region.
Best regards,
Ramesh P. Singh
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Kishor
Jaiswal [Saturday, February 02, 2002 12:00 PM]
Dear Sirs,
As you might be knowing that Probabilistic Seismic hazard
estimation has been a well established tool now for hazard estimation
of the region. It can be further used to develop probabilistic maps.
Such maps are already in use in US and many countries now.
These maps are prepared for Design basis and Maximum credible events (
10
% and 2 % prob. in 50 yr)
Such maps are already developed for Indian region by Prof. Harsh Gupta
(GSHAP program) However,
1. They have used the attenuation relation given by Boore
and Joyner (1981) applicable for Western North Africa. for entire Indian
region.
2. Background seismicity is not included in the hazard estimation.
( ie. Hazard values are available for regions where past
seismicity is known and no estimation for region of unknown seismicity
...remember Latur event???)
3. No uncertainty analysis for beta and nu values. For most of the
peninsular India region, underestimation of b-value which heavily
contributes to the final estimates.
4. Uncertainty in attenuation characteristics for regions with
different tectonics are not included.
5. Local Soil amplification factors are not established which are
important in near source events and thus underestimates the hazard for
the
region.
But importantly, this map provides a reasonable picture of hazard
in the region.
Following are the problems we face, when look in to the hazard
estimation of the shield areas.
1. Scarcity of Data to avail at seismicity parameters in case of no
historical events.
2. Unavailability of Established Attenuation relation for region
3. Uncertainty in Mmax or slip rate prediction.
Problem 1 can be solved when we look into the area of similar
tectonics such as worldwide SCRs. The CEUS has the similar problem but
the
they have developed models based on SCR worldwide and uncertainty analysis
for evaluation of seismicity parameters has been carried out based on
different models. (Taking 3+, 4+, and 5+ events and applying the
completeness test and evaluating the a and b values using Weichert method.
Problem 2 can be again solved using the attenuation relation
developed for shield regions of other SCRs. Such relations are aleady
been
develped in US by Toro (1997) and Frankel (1996) can be used with
including the epistemic uncertainty. Other relation is given by Free et
al. (1998) etc. can be used for SCR. Ofcourse we don't have established
relation for near source region ie. < 50 km region but there are models
developed for nearsource groundmotion based on Strong motion records in
WUSA.
Exact identification and location of active faults may take
million years but as you mentioned- the lineamants maps can be used in
this regard. The Mmax and or slip rate can be used to evaluate the
possible activity in the region. Use of different scenario for considered
zone based on rupture area or rupture length can be developed and the
corresp. prob. evaluation can be done.
All in all, we need to have efforts from geologists, seismologist and
earthquake engineers to develop "probabilistic hazard map of India".
One of the other solution is-
One can look in to the development of Seismic Microzonation studies and
prepare city-wise hazard maps with established soil amplification factors
based on shear wave velocity models and with due consideration of near
source events for known faults. Preparation of deterministic as well as
probabilistic map for large metropolitan areas can serve the purpose to
both the designers as well as the policy makers.
We should have seismic hazard map for atleast large metros so that people
can know what is the overall risk they can have....
(when they don't want to trust on Engineers ??)
The main problem what I see is,
There is a huge gap between geologists, seismologists and engineers when
information sharing is concerned.
Coordinated efforts has not been attempted by these people for common
goal
and this may be the reason for the current "stage a" zoning
map of India.
With Warm Regards
kishor
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Prachee
Dhavlikar [Thursday, January 31, 2002 7:16 PM]
Dear
organizers and colleagues,
I would like to make a suggestion:
The recent earthquake at gujrat made me ponder over many points.
Malpractices and igorance of earthquake detailing were among the main
factors responsible for the disaster. Which could have been avoided. But
an important point which I want to mention is that of soil structure.
I live in Pune city,which comes under the zone III as well as Ahemdebad.
Though the zoning has been done with respect to the earthquake intensity,
it does not at any time consider the soil characteristics. To elaborate
it further, Pune lies on the Deccan Plateau which has Basalt underlying.
Whereas Ahemedebad sandy soil underlying it. If we consider liquefaction
of soil, the effect of similar magnitude earthquake in Pune and Ahemedebad
will have different implications on the behaviour of superstructure. Zoning
therefore needs to be based also on the soil characteristics. Or
while doing analysis, ie IS1893 or IS 13920 should mention an additional
check to account for this effect. I have mentioned this points in one
of my papers published in an journal in Pune. Unfortunately I have never
had the time to investigate or study this matter in detail. It would be
interesting if someone does this study, so as to quantify or rather qualify
the suggestion I have done. Information would be most welcome
Regards
Prachee Dhavlikar