Risk Assessment:

"Earthquake”, the very mention of the word immediately conjures up pictures of the ground shaking and massive fissures in the earth opening and swallowing up people as they struggle for their lives while nearby buildings are collapsing and crushing cars. We've seen it many times in the movies, but never has one subject been of such interest, to so many, as seismic safety is to the residents who live along California's fault lines. To us, this is perceived as a major threat to our lives and livelihood. In just the past five years we have witnessed two massive earthquakes in California: the Whittier Narrows in the Los Angeles basin in 1987 and the Loma Prieta in the Bay Area in 1989. These two events represent a substantial source of dreaded fear in all of us. But just how life threatening are earthquakes and how much should we do to protect ourselves from this devastating, unpredictable natural disaster? These questions are at the very heart of "Risk Assessment".

Currently, before numerous city councils is the task of complying with a state mandate to implement a program to lessen the threat to human life as posed by unreinforced masonry buildings during an earthquake. It's the State's opinion that these buildings represent a tremendous threat to our lives and should be the focus of considerable attention. It's remarkable that, even at this level of government, no one has sought to determine just what the real risk to life is from earthquakes and how that risk compares to some of the other dangerous things that we do every day before enacting legislation, Richard Wilson of Harvard University, speaking on risk assessment, put it this way:

"Every day we take risks and avoid others. It starts as soon as we wake up. One of us lives in an old house that had old wiring. Each time he turned on the light, there was a small risk of electrocution. Every year about 200 people are electrocuted in the United States in accidents involving home wiring or appliances, representing a risk of death of about one in a million per lifetime. When we walk downstairs, we recall that 7,000 people die each year in falls in U.S. homes. But most are over 65, so we pay little attention to this risk, since we are younger than that.

How should we go to work? Walking is probably safer than using a bicycle, but would take five times as long. A car or, better, public transport would be both safer and faster. Expediency wins out and the car comes out of the garage (50,000 deaths annually from cars). The day has just begun, and already we are aware of several risks, and have made decisions about them."

Most of us act semi-automatically to reduce our risks. We also expect our government to minimize the risks suffered by its people, subject, of course, to overriding economic or other constraints. Risk assessments, except in the simplest of circumstances, are not designed for making judgements, but to illuminate them. To effectively illuminate, and then to minimize, risks requires knowing what they are and how big they are.

Quite often, the public demand for protection against dreaded risks disregards the real danger to human life because of the disastrous drama of the event. Severity of risk is not always the primary criteria that we use to decide which hazards we will abate or mitigate. Earthquakes, in which millions of dollars of property damage occur in the span of several seconds, and receive tremendous attention from the media, are perfect examples of this vein of thought. Public opinion, public perception, and existing legislative mandates are just some of the elements that are to be considered by the city council in their decision making process.

Obviously, our perceptions are a strong and compelling factor in determining what risks government will address. Popular opinion shows that the we consider earthquake damage to pose far greater risks than some very high risk activities that we willingly participate in everyday --things like smoking, drinking and driving and disregarding the danger associated with boating and snow mobiles. In addition, legislation from the State requires that local governments take action to reduce seismic hazards resulting from unreinforced masonry (URM) buildings, simply because they represent one of the sources of loss of life during an earthquake. The State legislators have given little or no weight to the actual risks posed by these structures.

Not only is it important to be accurate in our assessments of the risk to human life, we must also establish priorities to address the most dangerous risks first. Our society and community only has so much money, people and time to act on reducing every risk that comes to our attention. If we acknowledge the fact that our community does not have an abundance of money to eliminate every hazard that has been identified, it is imperative that we, through the judgment of our city council, develop a consistent, scientific method to identify and evaluate risk. It's important to promote an inquiry that will assist us in pursuing a rational plan to address the worse risks first.

Risk Comparisons and Perceptions

In the process of mitigating any risk it is always helpful if not considerably instructive to conduct some comparisons and contrasts. As members of a technically advanced society, we are outraged by the catastrophic risks posed by air pollution, nuclear energy and, closer to home, un-reinforced masonry buildings. We demand from our government representatives, legislation to protect us, that we should not have to suffer exposure to these catastrophic, uncontrollable, inequitable life-threatening hazards; yet we rarely mention concern for the ongoing threats to our daily lives that pose far greater dangers. Below is a brief comparison of some of the risks that we face every day, nationally, as compiled by Wilson and Crouch of Harvard University and the earthquake data is taken from the Waverly J. Person report on Significant Earthquakes of the World, 1987.

One thing that is very clear about our perception of comparative risks, is that we don't always worry about the risk averaged over time, like smoking or downhill skiing, quite as dramatically as we do the risks that are sharply peaked in time, like volcano eruptions and nuclear accidents. Wildavsky in American Science commented as follows on this state of affairs:

“How extraordinary! The richest, longest lived, best protected, most resourceful civilization, with the highest degree of insight into its own technology, is on its way to becoming the most frightened.

Is it our environment or ourselves that have changed? Would people like us have had this sort of concern in the past? ...Today there are risks from numerous small dams far exceeding those from nuclear reactors. Why is the one feared and not the other? Is it just that we are used to the old or are some of us looking differently at essentially the same sorts of experiences?”

Quite a bit of research has been done in an attempt to answer such questions by examining the opinions people express when they are asked to evaluate hazardous activities and events. This inquiry has attempted to develop some techniques for assessing the complex and subtle opinions that people have about risk. Researchers have sought to discover what is meant when the public says that something is "too risky" or "not risky" and what factors are universal in those perceptions. The basic assumption underlying this research is that regulators of public health and safety need to understand the ways in which people think about and respond to risk.

The overwhelming conclusions reached by the analysts show that the greater the sense of "dread" or the more uncontrollable, catastrophic, involuntary aspects characterizing the event, the higher was the demand for legislation to eliminate the risks. This end of the spectrum included such events as nuclear weapons' fall-out, electric fields, radioactive waste, pesticides, asbestos insulation, railroad collisions and the sort. The other end of the spectrum of hazardous events which did not receive an outcry from the public represented the "known" risks or those that were old, individual, controllable, and certainly not catastrophic. These risks included deaths from fireworks, bicycles, electric appliances, downhill skiing, trampolines, chainsaws and skateboards. The selection of what was deemed "important" risks and the disregard of the "unimportant" risks had no bearing, whatsoever, on the actual threat to human life. They found that the more "terrible" the event, the more regulation was requested. This is extremely evident in our present search for legislative language in the preparation of the seismic retrofitting ordinance before our city council.

In spite of the documented hazards associated with the actions listed in the above chart, the "dread" associated with them cannot compare with the horror of recalling the tragedy of the Whittier Narrows Earthquake of 1987 in the Los Angeles area. More recently, we recall the 6.9 magnitude Loma Prieta earthquake that shook eight Bay Area counties as we were settling in to watch the 1989 World Series. We collectively perceive seismic events as fearful, uncontrollable catastrophes that snuff out lives, inequitably and without notice. These elements which describe our perception of earthquakes represent a high order of "dread". The surprising data regarding loss of life associated with earthquakes, however, is far from what we expect. The California Department of Insurance, California Earthquake Zoning and Probable Maximum Loss Evaluation Program, compiled some interesting data which says a lot about the risk to life.

Specifically, the October 1, 1987 Whittier shock, which registered 5.9 on the Richter scale and resulted in damage to more than 10,400 buildings, unexpectedly claimed only 8 lives. Three days later, an after shock of 5.6 magnitude claimed additional structural damage and accounted for one more life; a victim of a heart attack.

In the continental United States and Alaska, earthquakes in 1987 claimed 11 American lives. In the entire world 1,098 lives were lost to earthquakes as reported in the U.S. Geological Survey publication "Significant Earthquakes of the World, 1987", by Waverly J. Person. By comparison, this represents a global risk to life of about 1 in 4 million. In our country alone, compared to our examples of daily risks, we are twenty times more likely to suffer the loss of our life by electrocution from turning on an appliance or light than we are from dying in an earthquake. If we were to extrapolate some risk figures for the city of San Luis Obispo, we would conclude that there is a risk of the loss of one human life in our town from home electrocution every 22 years. And similarly, based on global statistics, there is the risk in SLO from earthquakes of one life lost every 89 years. Additionally, if we were to factor in only the risk of fatality from damage to an un-reinforced masonry building, (assuming that 1/4th of all fatalities in an earthquake resulted from URM failure) we would expect to see one life lost in SLO every 1,777 years.

Nonetheless, the images of devastation to buildings and property, far out-shadow our actual perception of the risk to human safety and life. Quite clearly, the need for incorporation of this statistical data in the drafting of the "Seismic Ordinance" is the grave responsibility of our policy makers.

Cost of Reducing a Risk

Another interesting and instructive way of evaluating risks is by comparing the amount people have paid in the past to reduce them. Researchers have shown that the amounts spent vary by a factor of more than a million. It would be possible for an American to save lives in Indonesia by aiding an immunization program at $100 per life saved. Our society is willing to spend more on environmental protection through the efforts of the EPA to prevent cancer (over $1 million per life) than on cures (about $50,000 per life). What this data suggests, is that the government could save more lives by directing its vast expenditures into the hospitals and funding the life saving medical procedures facing the "terminal" patients that a cure exists for than by expending public funds to reduce certain elements in the atmosphere. This ratio is very much in accord with the maxim "an ounce of protection is better than a pound of cure". (1) (8)

Economists argue that efficiency depends on adjusting society until the amounts spent to save lives in different situations are all the same. It seems, though, that society does not work that way. Quite evidently, we attach greater meaning to the dramatic loss of life than we do the mundane. Invariably, we will vote to spend millions to protect against the dramatic mortalities, while funds allocated to protecting against the death from trampolines and skateboards, for example, is virtually ignored by comparison. Even, though people are aware of the order of magnitude of these differences, they support the cost of protection from "dread" versus "known". Nonetheless, providing this information to policy-makers is essential for an informed decision.

Standing before our City Council, is the decision as to the nature of the structural analysis that will be required for city building officials to adequately assess the relative weakness of each URM in San Luis Obispo. There is a considerably wide range of engineering reports that could be required by the proposed ordinance. The scope could run from an extremely detailed quantitative analysis which tested the materials and recommended restructuring or at the other end of the scale, it could be an analysis which qualitatively assessed the structural liabilities of each building in question and made probability recommendations regarding its retrofitting. Naturally the cost impact of these two methods of analysis is dramatically divergent. If we were to calculate the cost, for example, of conducting a quantitative engineering analysis of every URM identified by the City of SLO, we could arrive at a cost per life at risk in SLO. Let us consider the following conservative assumptions.

1. There are 100 buildings subject to a detailed engineering report.
2. The average cost of a structural analysis is $5,000 per building.
3. The probability of mortality from earthquakes is 1 per million (1 x 10 ^-6).
4. The population of San Luis Obispo is 45,000.
5. The entire population of the city is at equal risk.

To calculate, we multiply the number of buildings times the cost of each report divided by the fractional probability of mortality to arrive at the cost per life at risk. The formula looks like this.

100 buildings x $5, 000 ÷ 45,000 x (1 x 10-6) = $11, 111, 111 cost per life at risk

This engineering requirement, if enacted in the form of a city ordinance, will represent a cost per life 11 times greater than that assumed by the automobile industry and eventually the consumer to protect life with air bags in cars which has been estimated at $1,000,000 per life saved. We are proposing through this ordinance to spend a lot of money to protect against a risk of high consequence but very low probability. Most important, these expenditures for engineering will not make any building safer, but will comply with the intent of the State mandate.

Another scenario which addresses the need to evaluate the areas of critical threat to life from our URM’s is to propose that each building owner conduct a qualitative engineering analysis. This would essentially be the opinions, without benefit of any testing or calculations made by a structural engineer of the buildings inherent strength. Using the same assumptions as before, except that the average cost of the engineering is $600 per report.

100 buildings x $600 ÷ 45,000 x (1 x 10-6) = $1, 333, 333 cost per life at risk

In spite of the relatively low cost of each report, when it is combined with the extremely low probability of harm, the cost per life at risk is still considerably high but dramatically less than our first scenario. Throughout this analysis, it is critical to acknowledge that the money spent in both scenarios, above, does not reduce the risk to human life from earthquakes. It is merely money spent to learn more about the buildings which are believed to be the source of mortality during severe seismic activity. The information gained, however, may be important to decision makers if it is used to prioritize risks so that the most dangerous buildings could be identified. Regardless, it is a cost which is affordable by the individual building owners to, first of all, comply with the State legislation aimed at mitigating the threat to loss of life, and secondly, it adequately provides sufficient information for the city building officials to evaluate and prioritize the structures most needing attention. A further aspect of protection of the public welfare might include some closer analysis of the buildings deemed to be the weakest after review of the engineers' qualitative appraisal.

What Are We Protecting?

Obviously, the conclusions drawn from this study address the concern for protection to human life. It is the purpose of the State mandate to enact local ordinances to "mitigate the loss of human life" from the collapse of URM's, not to structurally reinforce them. Damage to businesses, buildings, freeways and homes are, obviously, going to be the consequence of any major seismic activity in our area, regardless of what structural changes we apply to our older buildings. Reviewing the data published in the San Francisco Examiner following the Loma Prieta earthquake in 1989, however, we can see that from all the damage incurred by thousands of buildings in San Francisco, the lives lost from URM's represented a very small fraction of the total casualties. Ten deaths were attributed to URM's when bricks fell off the buildings, no URM's collapsed. More than 20 times that number were killed in the collapse of freeways. In light of the limited damage to URM's in San Francisco, it might be concluded that we were spending millions of dollars to reduce the damage to the structures but not to significantly protect from the loss of life.

The responsibility for protection of the public welfare rests with the policy makers at the local level. The city council and its supporting divisions and staff members must use a scientific basis for risk assessment, in order to set priorities, tailor regulations and make decisions at particular sites. The tendency to include the emotional perception of harm, as perceived by the public, to protect against this hazard is always present to some degree. We know that the public often lacks certain information about hazards. However, their basic conceptualization of risk is much richer than that of the experts and reflects legitimate concerns that are typically omitted from expert risk assessments. The risk analysis should not attempt to overstate or understate threats, but rather to give a best estimate and the range of uncertainty. Our policy makers in the City Council can choose the proper amount of conservatism in setting the standard. Each side, policy maker and public, has something valid to contribute and each side must respect the insights and intelligence of the other.

The city can do much to improve public understanding of the meaning of risk assessment and risk management. In so doing, they can find solutions to the problems of mitigating the risks consistent with the parameters of limited private funds and with full regard to our experience of the historical threat to life posed by this one event.

William Dexter is a local Construction Failure Analysis Consultant who has served in the leadership of community business associations and national professional organizations.