By: Robert Merkel, Associate, Thornton Tomasetti
Last month’s earthquake in central Italy is yet another reminder of the devastating impacts earthquakes can have on communities, causing loss of life, loss of property, and widespread socioeconomic disruption. Over the last two decades, earthquakes have caused almost a million deaths and hundreds of billions of dollars in economic losses. In light of such figures it seems natural to ask, “Can you earthquake-proof a city?” On a recent episode of BBC World Service’s The Inquiry, four experts were asked that very question. Their thought-provoking comments touch on a wide range of issues faced by researchers, design professionals, and policymakers working to make cities safer against earthquakes.
So, can you earthquake-proof a city? That’s a somewhat complicated question, analogous to a query such as, “Can you crash-proof a car?” To answer requires clarifying what we mean by “crash-proof.” Do we mean “prevent loss of life?” Or, for example, is the expectation that all risk of damage be eliminated? The former option may be theoretically possible, though perhaps not always economically viable, particularly for a car (or building) that has already been built. The latter performance goal is probably not realistic, but it may be possible to alter designs to reduce (but not eliminate) the amount of damage expected.
We do currently have reasonably adequate engineering knowledge to design buildings and infrastructure so as to minimize loss of life in earthquakes. This is the basic premise of most modern building codes. Where those codes have been rigorously enforced, we have seen dramatically better outcomes in recent events. In the podcast Dr. Emily So draws an interesting comparison between the 1999 (M7.6) Chi-Chi earthquake in Taiwan and the 2005 (M7.6) Kashmir earthquake in Pakistan. In Taiwan, a place with reasonably modern and well-enforced building codes, approximately 2,000 people died. That’s a lot, but not when compared to the 86,000 dead from the earthquake in Pakistan, where there was relatively poor code enforcement. A similar comparison can be made between the Christchurch, New Zealand events of 2010-2011 (M7.1, M6.2), which left fewer than 200 dead, and the 2010 earthquake in Port Au Prince, Haiti (M7.0), which killed more than 300,000. The differences are not subtle. Death-toll outcomes are orders of magnitude better in places with modern building codes and good code enforcement practices.
However, designing according to modern codes is really only the start. Today’s building codes generally do a very poor job of minimizing loss of property in earthquakes. Even in the best buildings constructed today, some amount of property damage is to be expected, and in some cases damage could be substantial. Furthermore, most building codes generally govern only new construction. There are vast numbers of older buildings built to less stringent standards that could exhibit more severe damage or collapse.
To highlight the lack of correlation between adoption of current building codes and protection of property, it is worth pointing out that the financial value of property damage losses in the recent Christchurch earthquakes actually exceeded those in Port Au Prince, Haiti, despite Port Au Prince having roughly six times the population and suffering an earthquake death toll 1500 times larger.
Without significant changes to current building practices, earthquake property risk will actually continue to rise as urbanization expands in earthquake-prone locations. Recent studies have shown that a major urban earthquake could impair more than half of a region’s building stock for months after the event. Thus, major shocks to local economies (and potentially also to international markets) can be expected in such scenarios if the status quo holds.
There are, however, important steps that can be taken at the public policy level to both raise standards for new buildings and address deficient older buildings. As Dr. Lucy Jones points out in the podcast, there has been notable progress in Los Angeles recently in addressing risks posed by some of the most vulnerable building types and in protecting critical infrastructure. There is, of course, still much to do, and in most instances the available financial and political capital are inadequate to effect the scale of change necessary.
Earthquakes and Insurance
Insurance plays a vital role in financing post-earthquake recovery. Therefore, it is important that earthquake risk not be judged a bad risk not worth underwriting. Rather, affordable, widely-availability insurance should be an important part of any urban resiliency plan.
Of course, insurers cannot be complacent about their earthquake risk underwriting. Simple indicators like year of construction and basic code compliance are generally not good indicators of expected property losses. Insurers should also be aware of the potential financial risks posed by subtle regulatory changes that may not permit completion of structural repairs after an event without also undertaking significant upgrades. Such sources of uncertainty can represent major obstacles to an efficient earthquake insurance program.
The good news is that most types of earthquake property damage are reasonably predictable and can be quantified by experts before an earthquake occurs. The tools available to engineers conducting pre-loss risk assessments have improved significantly in recent years, enabling more transparent loss estimates that provide actionable information to stakeholders. Such information can, for example, be used to prioritize structural retrofit objectives. That same information can also be used in the design process to ensure that a new or retrofitted building meets or exceeds expected performance goals, which can be voluntarily set beyond minimum code requirements.
Insurers can use pre-loss engineering data (such as PML estimates, average annualized loss estimates, building performance ratings, etc.) to achieve more rational pricing of earthquake insurance. Such practice might in some cases provide competitive advantages when underwriting individual policies, particularly for high-value assets. More importantly, insurance portfolio risk uncertainty can be reduced when policies underwritten using pre-loss engineering evaluations are aggregated. Furthermore, a system that more transparently links expected losses to insurance pricing could enable insurers to incentivize earthquake risk reduction. Such incentives could provide significant leverage toward better managing and potentially reducing risks posed by future events.
So, while it may not be possible to earthquake-proof a city, there are valuable opportunities for insurers to work with engineers, property owners, and other stakeholders to “earthquake-prep” a city. Much can be done to mitigate the likely impacts of the next big event.