Earthquake Protection Systems_9 pptx

Urban planning departments are usually a part of local or regional government,and activities of the management of private building stock, seismic design codeenforcement and other local g

in e-commerce or use the internet for essential business communications needdisaster plans and back-up servers located outside the region likely to be affected

by earthquake Cellular phone networks have also been found vulnerable todisruption in major earthquakes Radio systems are less vulnerable to earthquakedisruption and may be worth installing as a back-up for communications Internalcommunications within an organisation can be maintained through UHF radiosystems – these are usually sufficient to cover a large site or campus City-widecommunications can be maintained on VHF radio, within specific wavebandsusually requiring a licence Conversations over a radio system of this sort areless secure – that is, other people can eavesdrop – but could be critical in anemergency A larger radio communication system can enable contact to bemaintained with places far beyond the area likely to be damaged in an earthquake

Maintaining Transportation Links

More serious disruption to an organisation’s operations may be the possibleenforced isolation if road and rail linkages are cut either locally or in the region.Inability to receive or make deliveries for any length of time may cripple the oper-ation of an organisation, particularly manufacturing operations unable to receiveraw materials or spare parts and unable to get finished products to market Anability to be flexible in transport mode will help, using road if rail links arecut and vice versa A storage capability to stockpile several days (or weeks)

of output, with freezing or preservative capabilities for perishable goods, maymake immediate despatch less critical Similarly, increasing the margins of stockoperations, although perhaps expensive in warehousing capacity, will make theoperation less vulnerable to disruptions in delivery of supplies

The less reliant the organisation can be made on continuous services beingprovided from outside, the less vulnerable it will be to disruption from a futureearthquake

6.3.7 Information Protection and Business Contacts

Many businesses, particularly small businesses, suffer badly from the loss ofinformation or records in the earthquake damage Files can be lost in destroyedbuildings, ruined by fires or by water leakages caused by the earthquake, wipedfrom computer memories or simply thrown into disarray by the overturning offiling cabinets Protection of commercial records from earthquake damage is animportant consideration It is possible to formulate filing and archiving procedures

to protect against earthquake-induced information loss A measure of protectioncan be ensured by keeping copies of important documents on back-up servers,

or physically in separate filing cabinets, preferably steel cased and low level.Archives may be safer if kept in a separate building Hard copies of importantcomputer files, and back-up disks, should be similarly ‘hard filed’

The chaos ensuing after a major earthquake is also extremely disruptive, againparticularly for a small business Communications may be cut and routines shat-tered If the business itself has lost its premises, or is forced to close temporarily,potential customers trying to make contact will be unable to do so Contactshould be re-established as soon as possible by informing customers and clientsabout the continued delivery of services and goods, and any relocation address,through advertising, mail, telephone or personal contact Disruption is likely to

be minimised if part of the organisation’s normal activities involve informingclients and customers, suppliers, subcontractors, staff and other business contacts

of emergency plans that would affect them, including information channels likely

to be used to confirm continued operations, contingency plans and enquiry tact points Information about an organisation’s emergency plans is unlikely tofrighten off customers and may encourage confidence if it is presented in thecontext of a range of activities being undertaken by the organisation to improveearthquake protection for staff and customers

con-6.4 Urban Risk Management

6.4.1 Urban Planning

The layout and development of cities, the location of infrastructure, key buildingsand utilities and the physical development of the built environment all affectthe consequences of an earthquake The urban planner, the regional planner,engineers designing the layout of utility networks, transportation routes or keyinstallations, and anyone whose job is to locate facilities within a city or whosedecisions affect the use of land, all have a role to play in reducing potentialearthquake impact

Urban planning departments are usually a part of local or regional government,and activities of the management of private building stock, seismic design codeenforcement and other local government measures for earthquake protection maywell be a central part of the responsibilities of an urban planning department Ifnot, the linkages between land-use master planning for earthquake protection andother urban planning protection measures and the control of building quality are

so interrelated that the development of effective earthquake protection measuresneeds a strong coordination between the groups with those responsibilities

As with all urban planning, effective management of the development of acity depends on understanding the processes that are making it the way it is Thetrends in land prices, the locational preferences for various industries, activitiesand communities, the demographic trends of the population and many otherfactors are all driving forces shaping the city Urban planning is the attempt todirect those forces using limited means and a small repertoire of legislative andeconomic powers The concerns of urban planning are many: to ensure a sanitary,pleasant and safe environment for the population, to provide adequate services tothe people and workers in the city, to enable the city’s activities to be carried out

more easily and to plan ahead for the future Many of the concerns of earthquakeprotection also parallel these objectives: limiting the densities of developmentand concentrations of population, protection of service provision and facilitation

of continued economic activities

By its nature, urban planning is long term Master plans have to encompassdecades of expected growth, and it is evident that earthquake protection is nec-essarily a long-term process

Adding Building Stock Management to Land Use

Where earthquake protection may be different to normal urban land-use planning

is in the emphasis on building stock management, i.e the influencing of theprocess of creation and maintenance of privately owned buildings in addition

to land use and location This process-orientated approach in combination withlocational aspects may require a slight reappraisal of planning methodology.Earthquake protection should be seen as an additional element of normal urbanplanning It should not be a separate activity from other planning operations, butrather an integral part of the planning process – another factor to be weighed inthe decision-making and balanced against other factors: when siting a new school

or planning a new residential suburb, earthquake risk should be weighed againstthe transportation implications, cost of land, suitability of the local environment,cost of providing services and so on Where there is a choice of sites with

an identifiable difference between them in earthquake susceptibility, this shouldinfluence the choice – if all other factors are equal the less susceptible site should

be chosen If not, the cost of building the school to higher standards of earthquakeresistance or imposing stricter controls on the residential structures should bebalanced against other costs and advantages of the sites Where a site of higherseismic hazard is chosen, the facilities and building stock built on that locationmust be built to higher standards of earthquake resistance Thus the integration ofseismic building code enforcement and building stock management with land-useplanning becomes critical

Microzoning and Vulnerability Mapping

From the discussion in the next few sections it will be seen that earthquakeprotection planning at an urban scale involves both the location of elements inthe city and the quality of elements in those locations Earthquake protectionplanning at the urban scale requires two additional maps to the urban planner’susual map collection:

(1) the seismic microzoning map of the geological earthquake hazards and (2) the seismic vulnerability map of the buildings and facilities of the city.

The addition of a seismic microzoning map in preparing land-use plans ordevelopment master plans may be fairly straightforward and comparable to other

preparation and study maps that contribute to the planning process However,the seismic vulnerability map encompasses the physical attributes of the buildingstock in a more comprehensive way than is usually needed for other planningactivities In addition to the characteristics of function, plot development, densityand perhaps number of storeys that are commonly used to map the building stockfor land-use planning, earthquake protection needs information on constructionmaterials, structural form, height and size, engineering design quality and ageand other broad indicators of seismic vulnerability (see Chapters 8 and 9 for vul-nerability classification of building types) with which to classify the earthquakeresistance of the building stock.

Building Stock Data

Information is needed across the city, from district to district, about the numbers

of different types of building classified by their seismic vulnerability togetherwith their functions and occupancy This is usually built up from building cen-sus data if it already exists or can be obtained by carrying out building surveys

on a street-by-street basis, but useful data on the physical characteristics of thebuilding stock can also be gathered from aerial survey interpretation, planningapplications or other documentation, or assumed from historical urban devel-opment patterns and existing land-use plans or zoned from other informationsources

Seismic vulnerability mapping and building stock inventories can be time suming if carried out in detail, but may only be needed at an approximate level

con-to give enough information for urban protection plans The broad identification

of the building types most at risk from a future earthquake and the parts of thecity which are likely to be worst affected may be relatively easily identified Thepolicies of upgrading the most vulnerable building stock sector and proposingland-use plans that reduce earthquake risk in the city are likely to be obtainablefrom relatively simple analyses

Land-use Planning and Seismic Microzoning

Some types of ground are safer than others in earthquakes In addition to thenumerous ground failures caused by earthquake vibrations, such as landslides,slope failures, liquefaction and rockfalls, it is well known that different types ofground vibrate more severely in earthquakes and so cause higher damage levels

to the buildings built on them Siting considerations for earthquake protectionare discussed in Chapter 7

Seismic microzoning, or the identification of various ground conditions in terms

of their earthquake hazard across an area at the scale of a city or conurbation,

is an important tool for urban planning to incorporate earthquake protection.Methods of microzoning are described in Section 7.4 The seismic microzoning

map, even if fairly coarsely defined, can be used as an additional informationresource for urban planners to incorporate earthquake protection considerationsinto their normal land-use planning decisions The map may define areas of likelyground motion amplification, potential slope failures, landslides or rockfalls andpotential liquefaction.

The delineation of the city and its environs, particularly its potential areas ofexpansion, into areas of relative severity of ground motion shaking likely to beexperienced in a future earthquake can help shape a safer city It may be possible

to avoid building on some areas of potentially higher hazard altogether – a zone

of very high hazard might be left as park area or the areas of city expansionmight be encouraged out in an opposite direction (through preferential provision

of transportation routes, urban services, etc.) By building on areas of potentiallylower hazard, future earthquake damage can be reduced This method of damagereduction has the advantage that if locational planning is possible, there is nodirect capital investment required to bring about increased safety There are anumber of indirect costs involved – land prices may be higher in one area thananother, or there may be increases in transport costs or needs for additionalinfrastructure – but in many cases the total costs to the community can be farless than those involved in the construction of stronger building stock Wherechoices of location are limited, or the arguments for locating in an area of higherseismic hazard for other reasons are convincing, structures or infrastructure built

in that location must be built to a higher standard of earthquake resistance Thematching of engineering code requirements and building stock management withland-use planning therefore becomes critical

High-intensity Amplification

The potential effectiveness of land-use planning for safety will vary considerablyfrom case to case Different types of ground affected by the same earthquakewaves may vary in their severity of shaking and consequent destructiveness byone or more degrees of intensity Stiffer soils, or hard rock, may be shakenwith ground motion of intensity VIII while softer ground close by, like shallowalluvium, is shaking more severely, closer to intensity IX From the vulnera-bility studies outlined in Chapter 9, this would mean that around 75% of weakmasonry buildings built on the soft ground could collapse, killing perhaps 14% oftheir occupants, whereas only 40% of the same building types built on the rockwould collapse, killing less than 5% of their occupants There is generally moredifference between the performance of different ground types at higher inten-sities, so for moderate levels of earthquake shaking locational planning is lesseffective in reducing losses But where high intensities are possible, the micro-zoning of a city or town can play an important part in earthquake protection Anexample of using urban land-use planning for earthquake protection is shown inFigure 6.1

In a case study of the effectiveness of strategies to reduce losses in the rapidly expanding city of Bursa

in Turkey, one of the options considered was locational control over the expected future growth of the

city suburbs The constraints on development are considerable, but if some of the predicted expansion

of the suburbs could be redirected away from their expected sprawl across the alluvial valley, and could

instead be encouraged to take place on the stiff soils at the neck of the valley floor, the city would be

significantly safer against a future earthquake A magnitude 7.2 earthquake occurring 30 km or so away

from the city in the year 2010 would be likely to cause an estimated 1200 deaths in the city If by then

land use controls have redirected the expansion, fatalities would be only about 980 - a reduction of 17%

in life loss This increase in safety would be independent of any changes in the quality of the building

stock, which would of course, give further safety.

Bursa 2010

(Expected Growth)

Bursa 2010 (Land Use Control)

Figure 6.1 Study of earthquake implications for planning of new city suburbs in Bursa, Turkey (after Akbar 1989)

Unfortunately the science of microzoning ground conditions and predictingtheir likely performance in future earthquakes is relatively young and thereare large uncertainties Estimates of likely response characteristics of differentground types are only approximate, and detailed knowledge of the sub-strataunderneath sites is difficult to obtain There are only a few places where earth-quakes have recurred and where detailed observations have been made of howthe ground conditions affect the intensity experienced In most other places, thedetailed effect of ground condition on ground motion severity can only be crudelyestimated

Frequency Characteristics of Soils

The information provided by microzoning studies cannot predict very accuratelythe severity of shaking and the amplitudes of acceleration likely to be experi-enced in a future earthquake, but it can be much more reliable in determiningthe frequency content of vibration due to different local ground conditions This

is important because certain building types are more vulnerable to different quencies of ground motion vibration than others (See Section 7.5.)

fre-Seismic microzoning can be used to ensure that a match does not occur betweenbuildings vulnerable to certain frequencies of vibration and ground conditions thatare likely to vibrate in that frequency range This is chiefly a problem for tallerhigh-rise buildings and soft soils that may amplify earthquake motions in the

long-period range To avoid buildings being damaged by resonance effects in

zones where the ground is likely to vibrate in certain frequency ranges, buildingsshould be designed either to have frequencies of natural vibration well outsidethe critical range or, more problematically, for the much higher seismic forcesthey are likely to experience An example would be a zone where restrictionsmight be imposed on building structures of 10 storeys high, likely to have anatural period of about 1 second, because the zone consists of deep deposits ofsoft soil that are also likely to have natural periods of vibration of about 1 second

so resonance would occur

Uncertainties about ground conditions and their likely performance in an quake may be too great for major decisions on location to be solely based

earth-on seismic safety cearth-onsideratiearth-ons, but they can add useful informatiearth-on to helpdecision-making for protection

Limitations of Land-use Planning

There are a number of other important restrictions to land-use planning as atool of the earthquake protection planner The first is that land-use planning isessentially opportunistic: there has to be a need for the location of new buildings(e.g an expanding city), a choice between alternative areas in which location ispossible, and a difference between the expected earthquake performance of thedifferent areas The second and possibly greater restriction is that land use has to

be controllable In many very rapidly expanding cities, principally in developingcountries, urban planning authorities have almost given up attempting to controldetailed land use, because the administrative framework for planning controls isimpossible to maintain The more stable cities, e.g in the developed world, havewell-established planning control mechanisms but the opportunity for changingtheir risk through land use is very limited because the city already exists and willlargely retain its historical layout

Land Price and Earthquakes

A major factor in shaping cities is land price Earthquake risk may itself changethe shape of the city to reduce future risk without planning measures Earthquakeshave been known to have marked effects on land price, changing the character

of urban areas in the longer term: poor ground conditions in a district of a city,highlighted by concentrations of earthquake damage, are likely to make that dis-trict less desirable and suppress land prices there.4 Land prices and commercialforces also change the nature of urban areas in other ways Higher land pricestend to make high-rise buildings more economic and this has implications forurban form, occupant densities and safety levels in the event of future earth-quakes Control of land prices directly is not normally part of urban planning indemocratic countries, but is strongly influenced by planning decisions, by zoningand by planning permissions Provision of services affects how desirable an area

is and residential densities may be influenced by levels of provision of utilitiesand other services Understanding the dynamics of urban land price economics

is often important in planning a safer city

Deconcentration of Cities

The worst earthquake disasters have occurred in ‘direct hit’ earthquakes – anearthquake epicentre directly underneath or very close to a large town Theconcentrations of people and buildings represent targets of high potential loss.Deconcentration of cities spreads the elements at risk by reducing densitiesand decentralising facilities Deconcentration and density limitations are desir-able in cities for other reasons too, including environmental improvements andlimitations on service provision Most urban plans already limit densities of devel-opment Limitations of density, height restrictions, plot development regulationsand other controls can all be used to limit concentrations of building stock It is,

of course, very difficult to change the densities of existing urban districts, andmuch easier to limit densities on areas of future development

Reducing Densities in Existing Cities

The densities of existing urban areas can be reduced by city authorities buying

up plots and demolishing to create open space among the blocks or opments at lower densities After some earthquakes in the past this has beenachieved by the city authorities buying up the sites of collapsed buildings and

redevel-4 After the 1985 earthquake in Mexico City, a number of banks relocated their office buildings from the badly damaged Reforma area to the more desirable and firmer ground condition of the nearby Polanco district to avoid problems of disruption to bank activities from future earthquakes This had

a significant effect on land price in the Reforma area and affected the development process.

making them into urban memorial parks.5 Such urban parks, even if they aresmall, add greenery to the city, help with urban hydrology, humidity and micro-climate, and provide areas for emergency facilities or population evacuation ortemporary shelter housing in the event of any future disasters Some cities nowhave large budgets for the re-greening of their built-up areas, buying up plots

as they become available on the open market In Japan, earthquake protectionobjectives (chiefly deconcentration for fire risk and the provision of refuge areasfor the population) have been set at the provision of 3 square metres per per-son of parkland in all major cities With the price of land in Tokyo currentlythe highest in the world, this is an expensive and long-term policy: TokyoMetropolitan Government has achieved nearly 1 square metre per person sofar, but other cities in Japan are closer to their target of 3 square metres perperson.6

Limiting Densities in New Settlements

In the planning of a new town in a seismic area it is important to limit thesize and potential for high-density over-concentration of development Densitycontrols include restrictions on building height, limitations on the plot ratio ofallowable development for any site, and limitations on access to basic services.Where direct density controls are not easily enforceable, other methods ofachieving lower densities include the design of street patterns, wider streets andlimiting plot sizes by physical planning means, using the design of the layout ofthe town and positioning of street furniture to maintain street frontages and tolimit plot developments

There are, however, no absolute levels or recommendations about density gets for earthquake safety Urban population densities vary considerably fromcountry to country and town to town, and the vulnerability of the building stock

tar-is the overriding factor in determining how much the population tar-is at rtar-isk fromearthquakes In a neighbourhood of fairly vulnerable buildings (masonry, forexample) the height and proximity of buildings, particularly buildings on a slope,should at a minimum be constrained to prevent one building collapsing onto orinto a neighbour The ‘domino’ collapse of buildings, particularly down a slope,has been one of the causes of high fatalities in earthquakes Similarly street lay-out road widths, particularly major routes needed for emergency access, should

be wide enough not to be made impassable by the rubble of a collapsed ture Vitally important routes should be wide enough to survive the collapse ofstructures on both sides of the road simultaneously

struc-5 After the 1985 earthquake, the sites of several collapsed buildings in Mexico City were turned into urban parks.

6 Itoh (1985), Ashimi (1985).

It is also important to reduce densities by designing open spaces in the city,particularly spaces within the built-up areas Such spaces also form safe congre-gation areas for the population, away from the possibility of injury from piecesfalling from the fa¸cades of buildings and, in areas at risk from fires, providesome safety refuge in the event of multiple fires.

Deconcentration and Fire

Deconcentration is particularly important to reduce the risk of fire spreading frombuilding to building in cities of flammable buildings The danger of conflagra-tions following earthquakes is particularly acute with timber frame structures orthose with combustible roofs: in such cases deconcentration becomes a majorearthquake protection measure The division of urban areas into small cells

by wide roads, rivers, parks and other fire-breaks limits the potential for flagration The chief risk for fire or earthquake disaster in many cities is insquatter areas or informal housing sector developments These are likely to bebeyond conventional planning measures, but general programmes to upgradesquatter areas should include reductions of density, access routes for fire andother emergency service vehicles, and discouragement of siting on hazardousslopes

con-Decentralisation of Major Cities

In many countries, there are efforts to decentralise capital cities and other majorregional centres There may also be programmes to reduce the rate of urbani-sation generally and to discourage large-scale migration of rural populations tothe cities Both of these measures reduce earthquake risk in a seismic region.Decentralisation of major conurbations reduces earthquake risk by reducing theconcentration of people and building stock, and earthquake protection is an addi-tional argument for decentralisation Decentralisation is commonly tackled using

a number of methods including the development of ‘satellite centres’ (local vices in the suburbs), ‘necklace’ development (suburban development beyondgreen belts), the promotion of secondary towns in the region, or moving min-istries and other key facilities to other cities, or promoting relocation grants forindustry and preferential provision of services in order to reduce developmentpressures on an over-centralised city

ser-After the city of Tangshan was devastated in 1976 by the most lethal earthquake

of the twentieth century, the Chinese planners rebuilt the city as three separatesmaller towns, several kilometres apart, partly in order to reduce the potentialfor an earthquake to cause another similar disaster.7

7 Wu Liang Yong (1981).

Protecting Urban Facilities

Planning new facilities and managing existing facilities in cities are a vital part

of the earthquake protection of the community Facilities provided and managed

by local authorities may include hospitals, schools, public housing, governmentbuildings, museums and many other publicly owned elements of the buildingdesign stock Other policies likely to be developed at city level include theconservation of historical buildings, and policies to maintain the cultural heritage

of valuable building stock, or to preserve the overall townscape qualities ofhistoric districts In addition, urban planners are likely to be involved in the sitingdecisions for many privately owned, large-scale facilities, like major industrialplants, shopping malls, office complexes and other major private developments.The location and design of public services and utilities, transportation systemnetworks, terminals and many other facilities are all a part of urban planning inits broadest sense

A checklist of urban facilities is included in Table 6.1 These community ities are important – some are critical – elements in the continued functioning ofthe urban society Protecting them against failure in an earthquake insures againstthe breakdown of urban society and the economic damage caused by loss of urbanservices

facil-Decentralised Facilities

At a strategic level, services provided by one central facility are always more

at risk than those provided by several smaller facilities This principle appliesequally to hospitals, government administration buildings and fire stations as itdoes to power stations, water treatment plants and airports

The collapse of the central telephone exchange in the 1985 Mexico City quake cut nearly all telephone communications in the city for a vital 48 hours Inthe reconstruction, the telephone system was redesigned using new technologyand dispersed, mini-exchanges to make the system less vulnerable to earthquakedisruption.8

earth-Networks such as water supply, piped gas supply or electricity may also benefitfrom being compartmentalised into relatively independent zonal blocks, so thatthe failure of any part of the network is localised in its consequences.9 Thedecentralisation of key services should be a primary objective for earthquakeprotection, or at least the protection against the failure of the service by the loss

of one or two elements within it

The creation of a robust system for each important urban facility listed inTable 6.1 should involve a vulnerability analysis of the facility itself For example:

8Aysan et al (1989).

9 Tokyo Gas Company has subdivided the pipeline system of the entire Tokyo metropolitan area into zonal blocks as an earthquake protection measure (NLA 1987).

Table 6.1 Usage classification of elements at risk.

Residential

Single dwelling

houses

Daily cycle, low occupancy

total building stock Multi-dwelling

apartment

buildings

Daily cycle, high occupancy

Shelter Significant percentage

of total building stock

Public buildings

Hospitals, clinics,

nursing homes

Permanent high occupancy

Critical – medical facilities

Expensive to replace Schools, colleges,

universities

Weekly cycle, high occupancy, children at risk

Public congregation points/aid

distribution centres/shelter

Public congregation points/aid

distribution centres/shelter

Expensive to replace

Museums,

galleries

Moderate occupancy

Non-essential Cultural value and

heritage Exhibits and contents may be irreplaceable

Public administration offices

Police station Continuous

level of occupancy

Critical – emergency services

Moderate financial loss Possible coordination role in recovery

Fire station Continuous

level of occupancy

Critical – emergency services

Moderate to high financial loss, especially if equipment lost No role in recovery Ambulance station Continuous

level of occupancy

Critical – emergency services

Moderate to high financial loss, especially if equipment lost No role in recovery

Table 6.1 (continued )

Public

administration

offices

Daily cycle, high occupancy

Important coordinating role

Important coordinating role in recovery

a large sector of the community

occupancy

No emergency role Provides employment

and sells products important for daily life

Shopping malls,

markets

High occupancy, daily and weekends

No emergency role Provides employment

and sells products important for daily life

Hotels, guest

houses, pensions

Permanent high occupancy

Temporary shelter for homeless

Economic generators (especially in tourist areas)

Cinemas, theatres,

sports stadiums, etc.

Occasional very high occupancy

Emergency equipment storage/morgue

Public morale Restaurants, night

clubs, bars

Occasional moderate occupancy

No emergency role Public morale

production)

Daily or permanent occupancy cycle

phase Factory

(non-essential

production)

Daily or permanent occupancy cycle

provide employment and continued income for many people

(continued overleaf )