Module Seismicity and seismic risk DECivil for civil

Module: Seismicity and seismic risk DECivil (for civil engineers) Mário Lopes (mlopes@civil. ist. utl. pt) Departamento de Engenharia Civil, Arquitectura e Geo-Recursos do Instituto Superior Técnico, Lisboa Bolonha, 3 -6 March 2014

2 – Natural effects, consequences and mitigation 2. 3 – Mitigation actions DECivil Ø Fault movements Ø Soil vibrations Ø Soil effects – landslides, liquefaction, subsidence Ø Tsunamis Ø Fires and Contaminations Ø Civil Protection

Fault movements - In general: do not built structures with supports on both sides of the fault. Identify fault traces and include in urban and territorial planning instruments. DECivil - Built with precautions (exceptional cases). Ex:

DECivil Alaska oleoduct: survived the differential movement between faces of a fault crossed by the structure. Denali earthquake 2003

Let the structure get damaged and repair it after the earthquake DECivil Railway line Istanbul- Ankara: it was repaired in 3 days after the Kocaeli earthquake, 1999

Soil vibrations In solid ground it is not possible to avoid soil vibrations, as they propagate everywhere. Therefore it is not possible to DECivil avoid the effects of soil vibrations, by far the most important of all, with instruments of urban and territorial planning. Since seismic waves travel at speeds of several km/s almost no human action is possible in the extremely short period between the initiation of the earthquake and the destruction it may cause.

DECivil EWS – Early Warning Systems These systems can provide a warning that na earthquake is about to occur a few seconds (5, 10, 20, 30 s) before it happens. They are based on accelerometers placed closer to the epicenter than the zones where the warning is to be issued

These systems allow the automatic shutdown (total or DECivil partial) of industrial facilities, seccioning of gas networks, reducing the probability of fires and explosions and more damage to electromechanical equipments, slow down of trains (this is the reason that led to the creation of the first of these systems in Japan), opening of doors of fire brigades facilities, and warnings to the population (sirenes).

Applicability of a EWS to protect Sines industrial complex DECivil

1 - Stations located about 20 km from seismogenic Zone of the Tagus River (North): Possible EWS in Sines Distance from faults to Sines ~ 90 km Distance from stations to faults ~ 20 km DECivil P arriving at stations in ~ 3 seg S arriving at Sines in ~ 23 seg 2 - Stations located onshore, at about 50 -60 km from interaction between plates zone at SW Portugal : Distance from active zone to Sines ~ 100 -150 km Distance from stations to active zone ~ 60 km P arriving at stations in ~ 8 -9 seg S arriving at Sines in ~ 24 -37 seg S speed propagation in Portugal ~ 4 km/seg P speed propagation in Portugal ~ 6. 8 Km/seg (according with data from recorded accelerograms obtained in the course of the M 6, 17 Dez 2009 earthquake ~ 60 km SW Portugal) 1 Sine s 2

Prevention It is the only way to avoid most effects of soil vibrations: DECivil to provide seismic resistence to constructions, lifelines, industrial facilities and even monuments. This is possible with the knowledge of modern seismology and earthquake engineering, by means of: - Seismicity studies leading to the definition of a design seismic action for engineering applications - Design of the built environment to resist strong seismic actions

Main actions that should be performed - Seismic evaluation of existing strengthening where necessary DECivil buildings and

DECivil Strengthened old house Old house not strengthened Earthquake of Faial, Azores, 1998

- Ensure quality of construction: check design and construction. Experience shows that damage is inversely proportional to the quality of construction. Scientific and technical knowledge is not enough, it is DECivil necessary to ensure its application in daily practice.

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- Seismic evaluation of lifelines and transportation networks, and strengthening where necessary DECivil

Sylmar substation, USA DECivil Before the San Fernando earthquake, 1971 Before and after the Northridge earthquake, 1994, (ag=0, 9. g) After the San Fernando Earthquake, 1971 (ag=0, 5. g)

- Seismic evaluation of industrial strengthening where necessary DECivil facilities, and

- Strengthening of monuments and buildings of high DECivil cultural value with low intrusive techniques, protect to the cultural heritage and identity nations peoples of and

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Soil effects - lanslides Avoid built in those locations – urban and territory planning instruments Increase stability of the slopes DECivil

Soil effects - liquefaction Avoid built in those locations – urban and territory planning instruments Reduce liquefaction potencial DECivil

Soil effects - subsidence DECivil Avoid built in those locations – urban and territory planning instruments If it is not of tectonic origin, it may be possible to avoid by compacting the soil

Tsunamis Avoid building in potentially flooded areas – usually does not compensate economically or it is not feasible DECivil Material losses – insurance Life saving – go to high ground before tsunami arrives Warning: Warning system. Not efficient near the epicenter. Earthquake: efficient near the epicenter if the population has been previously informed

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Fires Build large gas deposits outside urban areas if possible. DECivil Design with increased reliability (Importance factor in EC 8) Prepare gas network for automatic seccioning in case of strong ground shaking (does not avoid but reduces gas escapes and dimension of fires)

Information to the population to know that gas and electricity must be switched off. Buy a device that automatically cuts the gas (California, earthquakestore) DECivil

Contaminations DECivil Design facilities with highest level of reliability If possible choose locations where impact is less, should a leak occur

Civil Protection In some countries Civil Protection agency has strong responsabilities in prevention. In others their work is essentially the Emergency action, DECivil this is, after the earthquake. Post earthquake actions come too late to avoid the worse, as this happens during or right after the earthquake. Therefore, the main action to reduce earthquake effects is prevention. Without it, in case of strong earthquakes in densely populated areas, Civil Protection tends to impotent due to the dimension of the catastrophe. However, even with efficient prevention, it is an important complement of preventive policies, which can not avoid all damage nor prevent that people get injured at their homes due to vibrations.

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