Despite a century of research into earthquakes, Earth scientists are still only beginning to understand how individual faults behave. Although many dangerous faults have been identified, which has helped countries to strengthen their infrastructure, a significant number of deadly earthquakes occur on faults that are either unknown or were not thought to be particularly dangerous. That knowledge gap was highlighted last year, when a group of faults not particularly high on China's list of hazards linked together in an unexpected manner to spawn one of the most deadly quakes in recorded history, claiming at least 70,000 lives in Sichuan province (see page 153).

Earthquakes clearly pose the problem of how to prepare for risk in the face of uncertainty. The answer is complex, but can be boiled down to a few fundamental principles that scientists and government leaders should take to heart. Develop a clear message about what is known and — just as importantly — what is unknown. Be forthcoming about mistakes. And use a broad set of tools to prepare for hazards — a strategy that will make communities more resilient to different kinds of threat.

Citizens are generally poor judges of the hazards they face.

Scientists must rigorously assess the limits of their knowledge and communicate them to officials and the public. Earthquake researchers in some regions are getting better at this. California, for example, is one of the best-studied regions in terms of seismic risk. Two decades ago, seismologists there began issuing semi-regular reports on the major threats. Early on, they adopted a relatively rigid approach based on the understanding that segments of the San Andreas fault tended to behave in certain set ways, with characteristically sized earthquakes. But over time, the data — and the reports based on them — have grown less definite. The most recent assessment, released last year, acknowledges the complexity and uncertainty of fault behaviour more than past reports.

As for public officials, they must admit their mistakes and seek to learn from them — a lesson powerfully demonstrated during America's bungled response to Hurricane Katrina in 2005. In Sichuan, a large number of schools collapsed in the quake zone and too few answers have been offered by political leaders there about what happened. Amnesty International reported this month, for example, that the Chinese authorities have detained parents who have demanded information about the collapsed schools that killed their children.

The Chinese government must be forthcoming about what happened if it and other countries are to learn from this incident. Engineers who toured the site noted that some types of school building along one of the involved faults did not collapse whereas many others did. Data about school construction would clearly help to save lives in future disasters: the survival of some schools shows that structures can be designed to withstand severe quakes even in regions with limited resources.

Scientists, government officials and the public must strive to make societies more resilient to earthquakes and other natural hazards. Social-science research shows that citizens are generally poor judges of the hazards they face: they think they are safe until disaster strikes. The obvious but difficult truth is that societies must prepare for disasters before they occur. That means raising public awareness of the need to do so, something that Japan accomplishes with its annual earthquake drill each September. California last year successfully staged its first such drill and is planning to repeat it in October.

With public support, government officials can guard against earthquake losses by taking a multipronged approach. Buildings codes and land-use regulations — when rigorously enforced — can make structures safer. And societies can improve their ability to respond to quakes by strengthening their emergency systems as well as their capacity for reconstruction. Such preparations will also help nations to weather terrorist attacks, climate change and many of the other threats present on this dangerous planet.