Authors of Seismic Design of Foundations: Concepts and applications, Domenico Lombardi and Subhamoy Bhattacharya, examine past disasters to share lessons learnt and look at how we can mitigate their impact going forward.
Slope failure near Sendai, northern Japan, after the 2011 Tohoku earthquake
- Updated: 26 October 2020
- Author: Domenico Lombardi, University of Manchester and Subhamoy Bhattacharya, Chair in Geomechanics at University of Surrey, UK
Natural catastrophes pose major threats to modern society and its socio-economic order. While some natural events, such as floods, hurricanes, and volcanic eruptions can be predicted or detected sufficiently in advance to reduce causalities and limit economic losses, earthquakes remain largely unpredictable despite promising new developments in early warning systems.
Progress is being made but there is a lot of work left to do
One way to mitigate the impact of earthquakes is to build resilient infrastructure which limits structural damage, saves lives, and reduces repair costs. Although countries with high seismic risk are increasingly embracing a culture of preparedness, some encourage retrofitting interventions through economic incentives. In Italy the so-called “seismobonus” provides tax deductions of up to 85% of the total intervention costs. However, crucial challenges still remain as retrofitting of buildings is not always possible or economically viable.
How do we prepare for future events?
Importantly, we can only
prepare for things we have experienced before. If one looks at the historical evolution of seismic design practice, it is not surprising to see that major advances have occurred after catastrophic events have revealed limitations in current practice. For instance, soil liquefaction was largely unknown before 1960s but became a major field of research after it caused widespread damage in the 1964 Niigata earthquake and 1964 Alaska earthquake. Today liquefaction-induced damage is still observed but its effects can greatly be mitigated through sound design practices and ground improvement measures. Similarly, tsunami warning systems were rare before the 2004 Indian Ocean Tsunami, but today they are deployed worldwide, potentially saving thousands of lives from future tsunami.
Every event has a cause
Sometimes earthquakes lead to a unique set of events that result in multiple concurrent hazards. This was seen after the 2011 Tōhoku earthquake, where a series of sequential hazards, including a strong ground shaking, a massive tsunami and a partial nuclear meltdown left far-reaching consequences, the effects of which have been felt as far as the Californian and Chilean costs.
Failing to prepare equals preparing to fail
Another challenge is posed by so-called “tail risk”. This arises from low-probability, high impact events. As we have seen with the recent Covid-19 outbreak, we tend to ignore, and consequently fail to prepare ourselves against events that are not readily available in our memories. Imagine what if a high-magnitude earthquake, with return period greater than 10,000 years, hits a region thought to be of low-seismicity due to lack of strong ground motion records. If such an event occurs in the proximity of a metropolitan area, or near a critical infrastructure, say a nuclear power plant or a major tunnel, its consequences could be devastating. In many aspects we live in the realm of uncertainty. Seismic engineers and analysts pretend to live in the realm of calculable risk. History, however, provides plenty of evidence that this is not necessarily always the case.
Introducing our book
Find out more about seismic design and risk assessment procedures in Seismic Design of Foundations: Concepts and applications
, available in both print
format. After providing an historical perspective on the development of earthquake engineering practice, the book presents, through numerous real-world applications, the state-of-the-art in engineering seismology and seismic hazard analysis as well as seismic design of foundations.