Shaken confidence

Flawed risk communication can be dangerous (10 minute read)

I experienced my first earthquake in the mid-1990s, when I was living in Christchurch. I remember sitting on the couch in my flat, when the ground began to roll, not unlike being on a boat rocked by the waves. It was gentle and steady, and I was more curious than afraid. Back then, Christchurch wasn’t known for earthquakes. The city experienced them occasionally, but the people I spoke to didn’t think they were anything worth worrying about.

Until I was 23, I lived in Auckland and never felt an earthquake. The upper third of the North Island – Northland, Auckland and the Waikato – does experience some earthquakes, but they are mostly small and not noticeable. As a child, I worried about volcanoes and nuclear war, not earthquakes.

Even after I moved to Wellington, I remained relaxed about earthquakes. I wasn’t entirely complacent, because I did have a box of earthquake supplies, but disasters didn’t intrude on my thinking. Then, in 2008, I watched a television drama called Aftershock, based on the scenario of a major earthquake in Wellington. It was the most terrifying thing I’d ever seen.

What made it so frightening was that I couldn’t distance myself from it. One of the plotlines involved a group of people working in an office building on The Terrace, just as I did. The group ended up trapped in a partially collapsed building, all but one dying over the many days it took for help to come. After watching the programme, I barely slept for the next couple of nights.

A few days afterwards, still feeling on edge, I brought a bag into the office. It contained spare shoes, bottled water, warm clothing, muesli bars, toilet paper, plastic bags, batteries, a small radio and heavy leather gloves. I felt a little embarrassed storing all of this under my desk, but it also made me feel better. I had done something, and that gave me reassurance.

Earthquakes are on my mind at the moment because I was recently reminded of the 2009 earthquake in L’Aquila, Italy. It is the deadliest earthquake to affect Italy since 1980, but that isn’t why I’ve been thinking about it. Following the earthquake, a number of scientists were arrested and then convicted of manslaughter. Their crime? Making falsely reassuring predictions prior to the earthquake.

Convicting scientists for manslaughter over earthquake predictions sounds as medieval as the city’s architecture. But there’s a little more to the story than that. It’s actually a fascinating and illuminating case study in risk assessment and risk communication.

I’ve never been to L’Aquila, but I’m lucky enough to have visited a number of Italian cities and towns. To someone from a country where little of our built history survives much more than a century, the way Italy lives with its past is enthralling. I don’t think I could ever tire of wandering the streets of Rome, where around every corner there’s another ornate church, ancient ruin or building which has undergone centuries of rebuilding and repair. Even the most insignificant towns cram the past and present together at every turn, in an intricate mosaic of history.

Two thousand years of history in a single image (image credit: Melanie Newfield)

I was shocked when I first heard that Italy was prone to earthquakes. The kind of buildings I’ve seen there don’t look as if they’d stand up to much shaking. There’s a lot of brickwork, plaster and stone – brittle structures which don’t flex the way that wood or steel does. Nonetheless, when I started looking into it, I realised that Italy is one of the more geologically unstable parts of mainland Europe. While the whole country isn’t considered at high risk, areas of high risk can be found from one end to the other.

Like New Zealand, Italy is close to the boundary of two different pieces of the Earth’s crust. Although it feels solid enough to us – most of the time at least – the earth’s crust is not a solid shell like an eggshell. It’s more like crowded lily pads on a pond, where the lily pads are all moving in slightly different directions under the influence of wind and water movements.

New Zealand straddles pieces of crust known as the Pacific Plate and the Australian Plate. The movement of these pieces of crust distorts the land and creates New Zealand’s geological instability. The situation may be even more complicated in Italy. It lies just north of the boundary of the African Plate and Eurasian Plate, but there are some smaller pieces of the Earth’s crust in the area too. The movement of a small section of crust to the east of Italy has created the ridge of mountains, the Apennines, which run down Italy’s spine.

When I wanted to understand what had happened with the L’Aquila earthquake, the first thing I looked at was how large it was. The earthquake was described as 6.3, the same as the devastating 6.3 earthquake in Christchurch on the 22^nd of February 2011. But I encountered a problem. I wasn’t entirely sure which scale was being used. In the past, I can remember earthquakes being measured using the Richter scale. However, many of the sources I see don’t state exactly what scale they are using. Were the Christchurch and L’Aquila earthquakes being measured on the same scale? Were they similar in size at all?

If I’m looking for reports on earthquake magnitude in New Zealand, I look at GeoNet, which is a collaboration between a science institution and a government body involved with managing natural hazards such as earthquakes. Geonet refers to using the Modified Mercalli scale, often abbreviated to MM. But the L’Aquila earthquake is reported on the moment magnitude scale, abbreviated to M_W. What does this mean? How do they relate to each other?

Many of us grew up hearing about earthquakes described using the Richter scale, but this is no longer used by geologists – unless it’s specifically requested by the news media. While the Richter scale is well-known, it works well only for certain kinds of earthquake, and today the moment magnitude scale is the most often used. However, there are some important elements of the Richter scale which still apply to the moment magnitude scale. Firstly, each numerical increase represents a 10-fold increase in size, that is, an earthquake of 7.0 is ten times an earthquake of 6.0, for example. Secondly, they are both measures of the energy released by the earthquake. Thirdly, there is a single value which can be applied to an earthquake. It doesn’t change if you measure it from a different location.

When I looked more closely, I found that the 6.2 figure for the Christchurch earthquake in February 2011 and the 6.3 figure for the L’Aquila earthquake were both measured using the moment magnitude scale, so they were directly comparable.

The Modified Mercalli scale is something quite different, though. It is a measure of the shaking intensity on the earth’s surface, so it’s a better representation of what people and buildings experience. Although there is some relationship between the energy released and the amount of shaking, the two are different. In September 2010, Christchurch experienced a quake of 7.1 on the moment magnitude scale, while the February 2011 quake was 6.3¹. But the February earthquake did much more damage. The reason is apparent from the Modified Mercalli scale. While in some places the shaking intensity of the September quake reached 9, in the city it was variable from 5-8. The February 2011 quake measured 8 throughout most of the city.

Partly, the greater shaking in Christchurch resulted from the location of the February earthquake, which was just a few kilometres south-east of the central city. Partly, it was because the February quake was shallower, 5 km deep compared to 10 km for the September quake. The deeper an earthquake occurs, the more energy it loses as it passes through the earth. In fact, both the February 2011 and September 2010 earthquakes were very shallow, as was the L’Aquila earthquake, at just over 9km deep.

There’s another apparent similarity between the February Christchurch earthquake and L’Aquila earthquake too. They hit residents and buildings which had already endured months of prior quakes. While the original September earthquake near Christchurch had been a huge shock, occurring on a previously unknown faultline, there were numerous aftershocks in the wake of the first quake and prior to the February 2011 disaster. The L’Aquila earthquake also followed months of earthquakes, although these were all smaller than the disastrous April quake – considered foreshocks rather than aftershocks.

This is where the scientists in Italy ran into trouble. Understandably, the series of earthquakes in early 2009 frayed nerves. The situation worsened at the end of March, when a controversial researcher predicted a major earthquake in the area. So, on the 31^st of March, Italy’s Civil Protection Department held a meeting in the town, involving six scientists² and a senior official from the department.

The scientists concluded that there was: no reason to suppose a sequence of small earthquakes could be the prelude to a strong event and that a major earthquake in the area is unlikely but cannot be ruled out. However, that wasn’t the message given to the public. Instead, the public service official said: the scientific community tells us there is no danger, because there is an ongoing discharge of energy. The situation looks favourable.³

Unfortunately, this isn’t true. The official’s statement was reassuring, but wrong. And when a major earthquake struck on the 6^th of April, many people didn’t take the kinds of precautions they might otherwise have taken, such as getting out of buildings which were likely to be vulnerable.

The desire to reassure frightened people is understandable, but reassurance has to be realistic. Not only is it dishonest to underplay risks, it can be deadly.

More of Rome, since I’ve never been to L’Aquila (image credit: Melanie Newfield)

It was unfair to target the scientists who had participated in the meeting. They couldn’t have predicted the major earthquake, and nor was their communication inaccurate. Indeed, their convictions were overturned on appeal and then quashed by Italy’s Supreme Court. There was more debate about the charges against the official who made the inaccurately reassuring statements and his boss, who may have been the originator of the statement about the earthquakes discharging energy. Eventually, the only conviction which stood was against the official, and neither he nor any of the scientists actually spent any time in prison. Still, the situation prompted a lot of concern about the role of scientists as advisers.

Sometimes, officials are faced with a frightened public and may even be frightened themselves. A situation like the early days of the COVID-19 pandemic was a good example. People were right to be frightened then. In the case of L’Aquila, scientists and officials thought that people were needlessly afraid, and wanted to reassure them. However, although they may not have thought a major earthquake was likely, they presumably still wanted people to take appropriate actions if there was an earthquake. What could, or should, they have done differently?

This is where the literature on risk perception and Peter Sandman’s work on risk communication offer valuable insights. One of the major factors which influence our risk perception is our feeling of control. It’s why most of us feel safer driving our cars than flying in an aeroplane. One of the best things to do, then, is offer people actions they can take to reduce their risk. I understood this when I packed up my bag to bring into the office when I was feeling scared about earthquakes. I couldn’t influence the earthquake, nor how the building survived it, but I could increase my own chances of surviving by having supplies, and my sense of control by taking action.

Likewise, even if the Italian official had still made his inaccurately reassuring statement, he could have achieved a different result if he’d recommended actions people could take to prepare for a major earthquake, and reminded them of what to do if an earthquake did occur. Had he done so, it’s unlikely that the whole legal drama would have occurred, and lives may have been saved.

Ironically, it is sometimes the fearfulness of government officials which prevent them from communicating this important information – they fear that the public will panic, even though the evidence suggests that this is extremely unlikely. And so they resort to false reassurance, when what they really need to do is trust the public to do the right thing when they are given accurate information.

1. Some sources give the magnitude as 6.2.

2. It isn’t clear to me whether the scientists were all employed by the department or only the official.

3. Some sources also suggest he actually made this statement before, not after, the scientific meeting, which makes the situation worse.