EARTHQUAKES AND STRUCTURAL ENGINEERING
By J. C. Branner
Dr. J. C. Branner
Stanford University, Cal.
The ____________Company, of which I am the chief engineer, proposes to build several reservoir dams in the states of ______________ and _____________. If the Seismological Society of America can give me or refer me to information about the frequency and character of the earthquakes in those states it will enable me to determine the types of structures indicated.
This letter, from one of our best and most trustworthy engineers, brings home to us very sharply the need of the kind of information asked for. Our reply to it was necessarily short and disappointing, both to the engineer and to us. Some of the things that might have been said are given here for the sake of the cause and for the information of those who, sooner or later, are likely to ask similar questions.
As every engineer knows, the data called for cannot be obtained by experimental work in laboratories or deduced from mathematical formulas, but they require observations covering wide areas and long periods of time.
Inasmuch as earthquakes are matters that concern the public in a large sense, one naturally expects to find information regarding them gathered and published by the scientific bureaus of the federal government; but up to the present time the federal government has not taken this matter seriously.
The earthquake of April 1906 shook California hard enough to awaken a wide and lively interest in earthquakes -- on the west coast at least -- and naturally enough the Seismological Society of America came into existence.
One of the chief objects of this society has been and is to gather and publish data in regard to earthquakes, and to use the data both for direct practical purposes and for the investigation of some of the larger problems of geology. But the collection of information on the west coast of North America in regard to earthquakes is not as simple and as easy as it looks at first glance. The difficulties are several kinds, and are here briefly mentioned in order that engineers may know why the required data are not available, and in order that these difficulties may be overcome as soon and in so far as possible.
First, the frequency of light earthquake shocks on the west coast is, in itself, a difficulty, for the reason that most people are accustomed to them, and there is therefore nothing either alarming or impressive about them, outside opinion to the contrary notwithstanding. It is a common experience to hear a remark like this in the middle of a conversation: "By the way, did you feel that earthquake last night?" and after a yes or no, the conversation goes on without further interruption. The general result of this attitude of mind is that most people think too little of the matter to formally report the time and intensity of the shock. It does not really seem to be worthwhile.
Another and more serious obstacle is the attitude of many person, organizations, and commercial interests toward earthquakes in general. The idea back of this false position -- for it is a false one -- is that earthquakes are detrimental to the good repute of the west coast, and that they are likely to keep away business and capital, and therefore the less said about them the better. This theory has led to the deliberate suppression of news about earthquakes, and even of the simple mention of them. Shortly after the earthquake of April 1906 there was a general disposition that almost amounted to concerted action for the purpose of suppressing all mention of that catastrophe. When efforts were made by a few geologists to interest people and enterprises in the collection of information in regard to it, we were advised and even urged over and over again to gather no such information, and above all not to publish it. "Forget it," "the less said, the sooner mended," and "there hasn't been any earthquake" were the sentiments we heard on all sides.
There is no doubt about the charitable feelings and intentions of those who take this view of the matter, and there is a reasonable excuse for it in the popular but very erroneous idea prevalent in other parts of the country that earthquakes are all terrible affairs; but to people interested in science and accustomed to the methods of science, it is not necessary to say that such an attitude is not only false, but it is more unfortunate, inexcusable, untenable, and can only lead, sooner or later to confusion and disaster.
The only way we know of to deal successfully with any natural phenomenon is to get acquainted with it, to find out all we can about it, and thus to meet it on its own grounds. That is the way mankind has succeeded thus far, and it is safe to conclude that it is the only way it will ever succeed.
In the first place, the great majority of earthquakes experienced on the Pacific coast are not dangerous in any sense whatever; while the suppression of information regarding them leads those who live elsewhere to the entirely natural but erroneous conclusion that they are all dangerous. The truth about the matter is therefore not to the disadvantage of the region concerned. On the other hand, if there are places so liable to destructive earthquakes that houses, dams, bridges and other structures should not be built in them, or, if built, must have specially constructed with a view to withstanding earthquakes, then we think the people should know where those places are. Certainly nothing is to be gained by shutting our eyes to the genuine dangers or by exaggerating or encouraging others to exaggerate perfectly harmless shocks into serious dangers.
To meet the practical problems of earthquakes we must find out about them; and we certainly cannot find out about them if we are not informed, or if we are misled or misinformed. We are convinced, also, that the terrors that earthquake have for mankind are largely attributable to our own ignorance. The more we know about them the less harm they can do us, and the less reason we shall have to fear them. So that, after all, we come down to this absolute necessity: in order to deal successfully with them, we must have trustworthy information in regard to the time, the place and the character of earthquakes.
The next question is, how to get information about earthquakes. That the information should be most valuable, it should be gathered over as wide an area an over as long a period as possible. And to that end it is necessary that we take the matter seriously, that we get all the information we can, and every tie we can, and that we keep up our observations right straight along, year in and year out, whether the earthquakes are big or little. The man who is not willing to report a shock unless it be one that knocks his house down and kills half of his neighbors, is not a man from whom we can expect much valuable stimulus.
Everything we know about the gathering of data goes to show that we should have, scattered over as wide an area as possible, as many observers as possible who will report their observations, whether they seem to be important or not. The notes should be sent to some central office where they can be correlated and turned to account, just as the observers of the Weather Bureau, scattered all over the country, send their records to central stations where useful deductions can be drawn from them.
Obviously the Weather Bureau, with its excellent organization and its agents scattered over the entire national domain, is in a position to record and report promptly and fully upon earthquakes. But unfortunately the suggestion that these agents should be required to report on earthquakes has not thus far received the support of the federal congress. And if the federal government will not gather the necessary data and furnish this much needed information, then we must gather it ourselves as best we may.
Left to our own devices and our own too slender resources, there seems to be nothing for us to do but to appeal to our colleagues and to engineers and educated people generally for help in gathering and publishing such observations. If we can get this cooperation, we be able in a time to answer intelligently such reasonable letters at the one at the head of this article. But we feel it to be our duty to urge upon these very engineers the great importance and necessity of their own cooperation. To the engineers all over the country, and especially the engineers of the west coast we say: "Help us an we shall gladly do all we can to help you. If you feel an earthquake, report the time, place, and intensity to the Seismological Society of America." Taken alone, single observations may not be of any great importance; but taken in connection with a hundred other observations, they may be very important indeed. We feel that this matter is well worth while and that it should therefore be taken seriously, not only by geologists and structural engineers, but by architects, by business men, by enterprises and corporations that use the services of engineers, and by all other educated people.
In the task we have set ourselves we need the cooperation of observers over a wide area. Without such cooperation the efforts we shall be able to make cannot be very effective. It is hoped, therefore, that very person who observes an earthquake at any time or in any place in America will send to the secretary of the society a note of the time of its occurrence and its intensity. These two points -- the time and the intensity -- are the most important. Anything additional will be helpful and welcome.
As for the time, it is not expected that it will be given with absolute accuracy. Even if one has no clock or watch at hand when a shock is felt, he usually has some idea of the time of day. When nothing closer can be given, don't hesitate to make a guess and send it in for what it is worth.
Finally, no one needs apologize for any fact he sends in. To our requests for information about earthquakes we are frequently told apologetically that "I don't know anything about earthquakes." There is but one reply to be made to such remarks, and that is that "we know precious little about them ourselves; we are just now trying to find out, and we want your help."