Multi-hazard analysis of earthquake shaking and tsunami impact

doi:10.1016/j.ijdrr.2018.05.023

International Journal of Disaster Risk Reduction

Volume 31, October 2018, Pages 275-280

https://doi.org/10.1016/j.ijdrr.2018.05.023 Get rights and content

Abstract

Tsunami damage on buildings in regions subjected to shaking is commonly modeled disregarding the occurrence of a previous earthquake and damages that have already occurred at those buildings.

In Portugal, there are studies for the regions of Lisboa, Setúbal and Algarve that access damages or vulnerability of buildings due to the action of tsunami waves. Even so, they never took into account that, if near to the epicenter, usually prior to the tsunami, there was an earthquake shaking capable of provoking some level of damages to the building stock in the affected area.

In this paper, we propose a way of combining earthquake shaking damages with tsunami damages – the aggregated damage. This is defined as an additive function. The aggregated damage of a building is the sum of damages caused by the earthquake plus those caused by the tsunami.

As for earthquake shaking damage assessment, we use a home-developed software model based on standard vulnerability indexes conveying fragility curves for 5 different damage states (DS_i), for reinforced concrete and other building typologies (only masonry is considered in the present case). The tsunami fragility curves corresponding to similar DS_i, were obtained from recent published literature where the main variable was the water maximum height reaching each building which was estimated using a Geographic Information System (GIS) approach.

Section snippets

Introduction and objectives

Damage on building stock and impact on humans (displaced persons, injured and deaths) has been widely studied and applied all over the world, where earthquake-prone zones and civilization are present [1], [2].

When tsunami damage estimation is to be determined (through simulators or numerical modeling), buildings are often considered to be “as new”, i.e. damages caused by the previous earthquake are not considered.

Off-shore earthquakes can generate large tsunamis that aggravate the effects of

Fragility curves for earthquake shaking

To exemplify this approach we use the Setúbal downtown area, 25 km south of Lisbon. Damages at buildings from shaking are estimated using the SERS-MU (Simulador de Efeitos para Risco Sísmico – Meio Urbano) software [13], with the latest Portuguese Census data (2011) [14] regarding residential dwellings and resident population, and then we add building polygons for better visualization of damages. GIS data was supplied by the Civil Protection in the Municipality of Setúbal (SMPC) and completed

Fragility curves for tsunami damage estimation

Recent interest in computing fragility curves for tsunami waves has grown significantly. Both empirical studies based on assessing the behavior during past events as well as experimental or analytical studies are being prepared. In this work we use the results obtained with the first method (Nanayakkara and Dias [19]). As far as the other methods, Petrone et al. [20] developed analytical studies for the impact of tsunami wave forces on RC frames.

Nanayakkara and Dias [19] presented fragility

Comparing results: illustrating example – Setúbal, Portugal

For a 1755-like event, shaking measured in terms of EMS-98 Intensities are VII-VIII at Setúbal [3] and tsunami wave height are set at 8.1 m using tide height and modeling data provided by Santos and Koshimura [22], so it may resemble reality considering a worst-case scenario. DTM were obtained from SRTM [23] (1-arc sec, resampled to 25 m resolution). Santos and Koshimura [22] calculated the initial sea surface displacement based on the fault parameters (source dimensions of 200 km by 80 km),

Discussion, conclusions and future work

This paper intends to show that multi-hazard considerations can have an important role in the overall evaluation of impact caused by natural or man-made catastrophes. We use a very simple model to convey this eventuality which is a heuristic approximation to aggravate the damage caused by shaking with the effect of tsunami impact.

As seen in Fig. 8 or by comparing Fig. 5, Fig. 6, Fig. 7, damages are quite impressive and tsunami cannot in any case be considered separately, if the area under study

Acknowledgements

We thank the Municipality of Setúbal (SMPC) for providing data on the building stock of the town.

This work is under the framework of Instituto de Engenharia de Estruturas, Território e Construção (ICIST) and CeRIS Research Units of Instituto Superior Técnico.

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View full text

Multi-hazard analysis of earthquake shaking and tsunami impact

Abstract

Section snippets

Introduction and objectives

Fragility curves for earthquake shaking

Fragility curves for tsunami damage estimation

Comparing results: illustrating example – Setúbal, Portugal

Discussion, conclusions and future work

Acknowledgements

Development of the openquake engine, the Global earthquake model's open-source software for seismic risk assessment

Nat. Hazards

New Tools for the Analysis of the Generalized Impact Earthquake Events

Review of the 1755 Lisbon Earthquake based on recent analyses of historical observations. In Historical Seismology: interdisciplinary studies of past and recent earthquakes

Severity and exposure associated with tsunami actions in urban waterfronts: the case of Lisbon, Portugal

Nat. Hazards Online

Multi-hazard loss estimation for shaking and tsunami using stochastic rupture sources

Int. J. Disaster Risk Reduct.

Seismic vulnerability and risk evaluation for old urban nuclei

Earthq. Eng. Struct. Dyn.

Macroseismic and mechanical models for the vulnerability and damage assessment of current buildings

Bull. Earthq. Eng.

Evolution of earthquake losses in Portuguese residential building stock

Bull. Earthq. Eng.

European macroseismic scale 1998 (EMS-98)

Cah. du Cent. Eur. De. Geodyn. Et. De. Seismol.

Software for multi-hazard assessment

Eur. Comm. Proj. MATRIX

A three-level framework for multi-risk assessment

Georisk: Assess. Manag. Risks Eng. Syst. Geohazards