SEISMIC_ZONING_AND_SEISMIC_HAZARD_(1).pdf

IQC 391 – I – 11 – 00003

AID – 391 – 14 – 00001

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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Disclaimer:

This Project is made possible by the support of the American people through the United

States Agency for International Development (USAID). The opinion expressed herein are those of the author(s) and do not necessarily reflect the views of USAID, A. A. Associates or

Techno-Consult International.

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

SEISMIC ZONING AND SEISMIC HAZARD

Prepared by : Dr. Syed Abulkhair Masroor

Revised by : -

Approved by : Azher uddin Khan

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

SEISMIC ZONING AND SEISMIC HAZARD

Table of Content

BACKGROUND ..................................................................................................................................... 5 1.0

BUILDING CODES ................................................................................................................................. 6 2.0

2.1 LIMITATIONS OF CODES

WORK DONE BY CONSULTANTS .......................................................................................................... 8 3.0

3.1 MONENECO FEASIBILITY STUDY 1984

3.2 NEAK FEASIBILITY REPORT 2004

3.3 DBC ENGINEERING DESIGN 2008

CONCLUSIONS ................................................................................................................................... 11 4.0

RECOMMENDATIONS ........................................................................................................................ 12 5.0

REFERENCES ...................................................................................................................................... 13 6.0

APPENDICES ...................................................................................................................................... 14 7.0

7.1 DUE DILIGENCE

COMMENTS .................................................................................................................................... 20 7.1.1

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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BACKGROUND 1.0

The area in which the proposed Diamer Basha Dam is to be sited is a well-known seismic province. The proclivity of the region to seismic action is well known and over the ages has been recorded through oral traditions, archaeological evidences, historical documents and instrumented graphs.

The area is placed in an eye shaped geologic island arc between the Eurasian and the

Indian tectonic continents with major faults running to the North and South. This

“Island” is variously known as Kohistan Magmatic Island, Kohistan Oceanic Arc or

Kohistan-Ladakh Island.

Since major part of the upper regimen of Indus River passes through seismically active provinces, any dam on the upper reaches of the river has to be designed to sustain major earthquakes with an acceptable level of damage.

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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BUILDING CODES 2.0

All past and present Provincial as well as National building codes have placed this area in moderate or high seismic zones.

For example, Seismic Zoning Map of Pakistan included in the Building Code of Pakistan

1986 by Ministry of Housing and Works, shows this area in Moderate Damage zone corresponding to intensity VII on Modified Mercalli (MM) Scale of 1931. The zoning map accompanying this document was the zoning map commonly in use up to 1999.

The Sarhad Interim Seismic Building Code (SISBC – 02) issued in March 2006 by the

Government of NWFP (now Khyber Pakhtunkhwa) prepared by the Earthquake

Engineering Center of NWFP U E T placed the region of Dasu which comprises the left bank of the river at dam site in zone 2B, as understood in the context of UBC – 97 on which the code was modeled. No comparable document was issued by the Northern

Areas govt which has jurisdiction over the right bank of River Indus at the site.

SP – 07 which comprises the seismic provisions of the current Building Code of Pakistan issued by the Federal Government, Ministry of Housing and Works also places this area in zone 2B in reference to the UBC 97. The code also has micro-zoning and the site of the dam is assigned a Peak Ground Acceleration PGA factor of 0.24g.

2.1 LIMITATIONS OF CODES

The published codes are geared to calculating loads on buildings that have a reasonable probability of being experienced by buildings during their design life which is usually understood to be 50 years.

For example, The Seismic Code of 1986 has a disclaimer that excludes large dams, nuclear power plants and facilities handling toxic chemicals from its purview. The code based its zoning on the simple premise that an area which has experienced an earthquake of certain intensity, is likely to experience it again. It explicitly denies use of any probabilistic method in defining different seismic zones.

SISBC – 02 states in its scope that it “… is intended to be used for earthquake resistant design of reinforced concrete, brick and concrete masonry structures”. Obviously, its use for large dam structures is precluded.

The scope statement of SP – 07 is the most restrictive and states that “.. bridges, dams, harbor structures, tunnels, pipelines, power transmission lines, power generation plants including hydel, thermal and nuclear power plants, gas storage facilities, special defence

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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The limitations of building codes are often explicitly stated but even where there are no disclaimers, it is generally understood that the earthquake parameters, usually in the form of PGA are to be applied for everyday structures governed by local jurisdictions.

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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WORK DONE BY CONSULTANTS 3.0

The first step in designing a large dam to resist earthquake forces is the assessment of the intensity and probability of occurrence of seismic events during the life time of these structures. A dam like the proposed Basha-Diamer Dam which can cause catastrophic damage to a large area in case of failure needs to be studied carefully before deciding on seismic parameters for design.

The consultants tasked with feasibility and/or design of the dam have been well aware of seismic nature of the region. Starting with the pioneering work done by MONENCO in

1984, through tender design by DBC, each consultants paid due attention to this aspect. As the work improved in quality and detail, the seismic assessment was also refined to reflect state of the practice.

3.1 MONENECO FEASIBILITY STUDY 1984

Montreal Engineering Company (MONENCO) in their work simply assumed a seismic horizontal acceleration coefficient based most likely on the seismic zoning map of that time. MONENCOs work was geared toward identification of possible dam sites for further assessment and may be regarded as pre-feasibility. The report deals rather cursorily with the task of seismic hazard assessment. However, considering the preliminary stage of work, more detailed study may have been deemed unnecessary.

3.2 NEAK FEASIBILITY REPORT 2004

NEAK Consultants in their feasibility report conducted a detailed study of the seismology of the area. The study is contained in Appendix IX to Volume IV of their report. The consultants conducted probabilistic as well as deterministic procedures to arrive at a

Maximum Credible Earthquake (MCE) Peak Ground Acceleration (PGA) of 0.4 and an

Operating Basis Earthquake (OBE) PGA of 0.21

Although the consultants did a lot of painstaking work in data collection and analysis, the report suffers from some basic flaws:

The historic data record of earthquakes does not extend to the major Kashmir earthquake of 2005 which has an epicenter within 100km of the site.

The analysis ignores the possible relevance of Main Boundary Thrust (MBT) which is a very major active fault and passes within 100 km of the site.

The near field possible sources of earthquake are not thoroughly investigated

The process for selection of time histories used for calculation of response spectra is not documented.

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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Since the work was done at a feasibility level, the details to which the consultants go are quite commendable. The report suggested further neo-tectonic studies at the detailed design stage, which would have helped make the work more complete. Installation of instrumentation to record seismic events was also suggested.

3.3 DBC ENGINEERING DESIGN 2008

When the Diamer Basha Dam Consultants (DBC) were entrusted the work of reviewing the feasibility and preparing engineering design for the dam, they entrusted the job of seismic hazard evaluation of the site to South Africa Council for Geosciences (SA CGS). The council submitted its report in November 2007.

The work done by the council is based on the work by NEAK consultants and subsequent field investigations by DBC. The report also refers original contemporary work on seismic hazard evaluation of this region by Mona Lisa.

The report posits that the Main Mantle Thrust (MMT) Fault is inclined so that although the trace of the fault is 46km away, it dips and passes right below the dam site about 20 km below the surface. The council recommended a deterministic maximum value of PGA =

0.46 based on rupture in the fault underneath the dam site.

There are a number of anomalies in the report which need to be pointed out here:

The report ignores any possible impact from ten out of twenty seismic sources including the active major fault MBT

An earlier version of the SA CGS report recommended a PGA of 0.61 [PoE Report

No. 5 September 2006] which was later revised to 0.46. The process by which this revision was affected is not transparently reported

Numerous active faults were discovered and documented by MR R. Van Der Vlugt of SA GSC [Annexure 1.3] but not further investigated by the consultants.

The PSHA is based using an approach developed by SACGS which is derived not on actual events but on the assumptions of probability of occurrence of certain fault ruptures by the investigator [Table 3.3.2.2.1]

In the Review of Seismic Risk Assessment by Mr. Inayat Ali which is included in the report [Annexure 1.2], it was determined that a 50km lineament passing very close

(less than one km) to the dam site delineates a possibly active fault. It was hypothesized that this “fault” may undergo a large rupture to cause MCE. This possible fault has not been further investigated by DBC.

The report gives no guidance on Response Spectrum to be used for seismic design.

Due to this lacking, the designers arbitrarily chose time histories for seismic analysis of the dam.

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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The process of determining the relevant seismic parameters can be regarded as deficient, considering the possible ramifications of incorrectly predicting seismic parameters for this major project.

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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CONCLUSIONS 4.0

Due Diligence Report is annexed to this report with comments. A number of non-conformances and incomplete items have been identified. Some of the non-conformances are trivial, but work is needed to remove all these non-conformances.

The major failing of the seismic hazard assessment process adopted for this project lies in incomplete site investigation of nearby faults to determine if these are active and relevant.

The report which itself calls for further study and investigation of discovered active faults, is concluded without any serious further investigation of the evidence. Inexplicably, DBC came to an abrupt conclusion [Annexure 1.4] that none of the discovered active faults were worthy of further investigation.

The process by which DBC issued the directive declaring some of the faults as inactive or not significant is not recorded and therefore, cannot be assessed properly.

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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RECOMMENDATIONS 5.0

Although the seismic parameters are not likely to change much from those used in design, more work needs to be done to improve confidence on design before implementing it for construction and to eliminate any doubts on the parameters. This will require both the field investigation of suspected near-field faults as well as desk study to include more recent earthquakes. Specially, the Kashmir earthquake should not only be included in the

PSHA, but the signature waveforms should also be studied to construct a more relevant response spectrum.

If possible, the tasks of assessment of hazard and design/construction of the dam to resist these hazards should not be made parts of the same procurement process to avoid conflict of interest. An independent agency should be assigned the task of determining the site specific parameters for seismic design prior to the main contract. The designers should then be asked to design based on the parameters determined by the agency.

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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REFERENCES 6.0

Building Code of Pakistan 1986 by Govt. of Pakistan, Ministry of Housing and

Works, Islamabad

MonaLisa, Khawaja, A.A., Javed, M., Ansari, Y.S. and Jan, M.Q. (2005). Seismic

Hazard Assessment of NW Himalayan Fold and Thrust Belt, Pakistan, Using

Probabilistic Approach. Proc. Pakistan Acad, Sci 42(4): 287-295.

Building Code of Pakistan (Seismic Provisions – 2007) GOP Min. of Housing and

Works, Islamabad

Geotechnical Earthquake Engineering by Steven L. Kramer. Prentice Hall/Pearson

Education Inc. 1996

ICOLD Bulletin 72 Selecting Seismic Parameters for Large Dams, Guidelines, ICOLD

Committee on Seismic Aspects of Dam Design, 1988

SARHAD Interim seismic building code VERSION 02, March 2006, by Earthquake

Engineering Center, NWFP Univ. of Engg. & Tech., Peshawar

SEISMIC Hazard Evaluation Studies, DRAFT report June 2006, by NESPAK 1-C- N, Model Town Extn., Lahore for GOP, Ministry of Housing & Works.

ICOLD Bulletin 46 Seismicity and Dam Design, ICOLD Committee on Seismic Aspects of Dam Design, 1983

ICOLD Bulletin 52 Earthquake Analysis Procedures for Dams State of the Art, ICOLD

Committee on Analysis and Design of Dams, 1986

RESPONSE SPECTRUM ANALYSIS OF CONCRETE GRAVITY DAMS INCLUDING DAM-

WATER-FOUNDATION INTERACTION By Arnkjell Lokke and Anil K Chopra. Pacific

Earthquake Engineering Research Center July, 2013 (PEER 2013/17)

A PROBABLISTIC FRAMEWORK TO INCLUDE THE EFFECTS OF NEARFAULT

DIRECTIVITY IN SEISMIC HAZARD ASSESSMENT By S K Shahi and J W Baker. Pacific

Earthquake Engineering Research Center October, 2013 (PEER 2013/15)

CURRENT SEISMIC SAFETY REQUIREMENTS FOR LARGE DAMS AND THEIR

IMPLICATION ON EXISTING DAMS Paper by Martin Wieland and R. Peter Brenner

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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APPENDICES 7.0

7.1 DUE DILIGENCE

In this report, the items listed in the Due Diligence Format are marked OK, NG, NR, or IC in the design conformance section , followed by the comment number in the comments column. The markings reflect the following:

OK The item has been adequately and comprehensively addressed by the designer as per current practice.

NC The item has been either ignored or inadequately handled by the designer

NR The item is not required for the design method adopted by the designer for this particular site

IC The item is addressed by the designer but not is deemed incomplete or needs minor adjustments or further work. This remark is invariably followed by comments.

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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Diamer Bhasha Dam Project Due Diligence on Design by DBC

Seismic Parameter Selection

S.No. Best Practice as per ICOLD Standards DBC Design Conformance

Remarks

1 Selection of Seismic Parameters General Have movements along faults and discontinuities in foundation been assessed for DB Dam?

Have sympathetic movements along discontinuities been assessed?

Have potentially active faults been examined and ruled out?

Have both seismic actions affecting both the main dam body and appurtenances been examined to include bottom outlet, spillway gates, control units, cofferdams and power supply been checked?

Especially for concrete arch dam like Bhahsa for case of equipment laden components has motion of equipment support used as input? This is most important for elements along dam crest where amplification of support motion must be examined?

OK

NR

NC

IC

2 Seismic Hazards Assessment Has seismic hazard assessment been made on DB Dam systematically i.e. taking into account following:

-key sources of earthquakes -characteristics of each earthquake such as geological settings, magnitudes and rates of ground motion -Appropriate empirical relationships have been employed for ground motion amplitudes or intensity analysis?

Has degree of uncertainty been examined on seismotectonic conditions and info available in the vicinity of the DB dam?

3 Regional Geological Setting Has tectonic, geologic and seismic evaluation been made on both regional (100 to 300 kms radius) and local levels surrounding DB dam?

While determining regional geologic setting factors such as geologic history of project area, regional physiographic features, geological formations been considered?

Has following parameters duly been collected evaluated and recorded for DB dam?:

-physiographic and tectonic settings -Geologic history

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Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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-geologic formations, rock types and soil deposits -Key geological features such as folds, fracture or joint patterns -regional tectonic mechanisms and associated faulting -Specific identification of faults / shear zones -Potential of these faults to generate earthquakes including fault history -Fault characteristic such as slip rate, slip per event, time interval between large earthquakes -Any eruption activity, geysers or boilers etc.

-Seismic studies conducted or anomaly surveys undertaken -Geo Magnetic or Geothermal data -Geodetic surveys indicating movements

4 Seismic History Has historical recorded earthquake data been acquired and examined?

Has probabilistic analysis been carried out based on historical data?

Has the data search extended to outside Pakistan (worldwide sources of seismic data)?

Has earthquake data been properly collected and presented to include epicenter locations, magnitude , time stamps, depth, mechanism, area influenced, surface effects, intensity of ground motion, comments on reliability of source, isoseismal contours generated plots based on instrument data?

In making seismotectonic interpretations has regional stresses at different geological periods been considered? Has stress measurements if any, types of faulting, definition of seismotectonic provinces, seismotectonic map etc taken into account?

5 Local Geologic Setting Has DB site specific data gathered to include:

-characteristics of ground motion expected -primary or sympathetic fault movements -data or reports from nearby projects, site visits and field truthing, material sampling and testing -Location and chronology of local faulting -Type and magnitude of displacements of faults, time of rupture, rates of activity, strain rates, slip rates and the like -detailed examination and analysis of local geology with joint system settings, bedding planes, dips, strikes, folds, highlighting intrusive or extrusive bodies

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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-Assessment of hydro geological conditions -Has hazards of seiches in long water body of reservoir been estimated?

-geological conditions assessments for foundation and abutments of DB dam In assessing local geology has stratigraphy / petrography of bedrock been properly assessed, has local and microtectonics been examined within the bedrock contour map?

6 Selection of Earthquakes For Analysis Has earthquakes been characterized for magnitude, acceleration, spectral ordinates, duration to be used as input for analysis?

Has either deterministic procedure or probabilistic procedure been used and with what justifications. Has advantages of using a probabilistic seismic hazard evaluation over deterministic approach properly been examined?

Have mathematical and statistical processes been employed to study relationship between ground motion parameters probability of exceedance for given intervals?

For Probabilistic approach if adopted have earthquakes been duly evaluated and documented for analysis within the band of minimum and MCE events?

If deterministic procedure is used then has evidence of movements been duly examined for Holocene, Pleistocene and Quaternary times?

Has rupture length-magnitude relationship or fault movement and magnitude relationship been used ?

Has following type of earthquakes been duly characterized and estimated for design of DB dam?

-Safety Evaluation Earthquake (SEE) -Operating Basis Earthquake (OBE) -Maximum Credible Earthquake (MCE) -Reservoir-Triggered Earthquake -Construction Earthquake -Design Earthquake for Appurtenant Structures

7 Seismic Evaluation Requirements Has basic seismic loads derived from SEE and OBE events?

Has it been ensured that spillway and bottom outlet are operational after seismic event?

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Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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Has consent been obtained with WAPDA for proper use of these earthquake events?

Has following seismic input parameters for analysis been adapted:

-acceleration time histories -spectral accelerations or peak ground acceleration What method adapted for determining these values?

Have mean annual exceedence probabilities (AEP) been worked out ?

Has ICOLD guidelines been followed wherein:

-peak vertical accelerations assumed equal to 2/3 peak horizontal accelerations -In estimating PVA has factors such as type of fault movement taken into account?

Has adequate seismic parameters used for dam (seismic) performance evaluations under SEE and OBE such as following:

-acceleration -velocity -displacement values -response spectra -acceleration time histories Has a combination of these parameters been used?

Has seismic evaluation parameters of SEE and OBE used in numerical analyses of DB dam?

Has ‘Source’ effects, ‘Transmission path’ effects and “Local” effects been examined?

Has factors such as direction of fault rupture propagation included in seismic studies of DB dam Have all factors affecting ground motions been considered?

Has PGA (Peak Ground Accelerations) been defined on outcropping bedrock and adjusted to account for specific site conditions as topography or alluvium where free-field accelerations generally contain more energies in the long period range than those on a rock site?

Has amplification of low frequency seismic waves as a consequence of soft sediments been examined?

Has attenuation relationships been studied? For surface sediments has spectra given been adjusted to the sediment deposits?

Has duration of shaking period properly assessed?

Has response spectra been characterized for SEE and OBE events?

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Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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Has acceleration time histories been compiled?

8 Factors Influencing Selection Of Seismic Evaluation Parameters Has influence of potential consequences of failure accounted for following:

-Failure of structure -failure of socio-economic component -Effect on population, infrastructure and properties impacts in downstream Has effect of Concrete Arch Dam type proposed for DB and its possible failure modes been accounted for in selection of seismic evaluation parameters?

Has overall stability, prevention of excessive cracking due to overstressing of concrete been assessed through finite element method numerical analysis?

Has peak ground motion parameters and response spectra been used to define seismic evaluation parameters?

Has need for Dynamic finite element response analyses been assessed as DB falls under extreme or high consequence or hazard class?

Has appropriate response spectra or acceleration time histories used to specify the Design Earthquakes w.r.t.

to for peak stress evaluation purposes?

Has three stochastically independent analysis proposed or for two components of horizontal motion and one vertical component?

Has vertical accelerations and its related amplification effects and effects of dam-reservoir interaction been duly considered ?

SEISMIC ZONING AND SEISMIC HAZARD

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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COMMENTS 7.1.1

1 The dam base has been examined for faults and discontinuities and none were detected. Therefore, there was no case for sympathetic movements and this was ignored by the designer.

2 There is no record of investigation of some potentially active faults. These have been pointed out, but not fully investigated by the designer. (SACGS Report)

3 The design at this tender stage is not detailed to the level where design of equipment foundations can be performed. This will obviously be done after selection of equipment has been finalized for procurement.

4 Although the geological settings and magnitude of the earthquakes in the region has been considered in terms of Richter Scale magnitudes, there is no evaluation of rates of ground motion.

5 Although most regional faults have been included, Main Boundary Thrust which is an active fault responsible for some major recent earthquakes and extends to areas that lie within 100 km of the dam site has not been considered. Some near field faults have been found but not fully investigated.

6 See 5 above

7 The area has no volcanic activity and crust at this point is very thick

8 The records need to be updated as the major Kashmir earthquake of 2005 is not included

9 Iso seismal contours have not been generated.

10 Some data has been gathered but not used in characterization process or design

11 The work is not done in as much detail as may have been warranted for this size of project

12 The deterministic evaluation is solely based on distance from the fault and magnitude of the earthquake. Other parameters are not considered.

13 The acceleration time histories used in design are selected arbitrarily and have no documented relationship to any actual or potential earthquake at dam site.

14 This important aspect is neither investigated nor included in any study.

15 Since the dam is to be founded at bedrock level, no layer of soft sediment need be considered.