Shaking the bowl of porridge: Site and Basin Effects on Seismic Hazard in Jakarta

Date & time

4–5pm 17 October 2017


Jaeger 1 Seminar Room, RSES


Mr Athanasius Cipta

Event series


 Antony Burnham

Jakarta city has been growing fast since the late 1960s and has become one of the most populous cities in Asia with the highest economic growth. Strong ground-motion has not shaken the city for more than a century, however, colonial era documents suggest that in 1699, 1780 and 1834, strong quakes shook and devastated the city.     


At the moment when the large earthquake shakes a basin, sediment inside this basin will be shaking accordingly. In the soft and thick sediment, seismic wave will be slowing down in velocity but the amplitude will be amplified. When we shake a bowl full of porridge, the more watery the porridge, the bigger the shaking suffered by porridge. Similar to what happened when earthquake shaking the basin, the softer the sediment, the higher the amplification can be expected.


Jakarta is a basin filled with thick soft sediment, so that, when subduction zone generates large earthquake, a high amplification may occur and great shaking is expected in this city. In our simulation indicates that intensive amplification occurs at spectral periods of about 2 and 5 second. This spectral period highly affects 20 and 50 storey buildings, or we can say that these type of buildings may experience heavy damage.


In the future, we wish our study can help engineers in creating building code that takes seismic hazard analysis into account.

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