Popular Science Monthly/Volume 69/September 1906/America and Seismological Research
|AMERICA AND SEISMOLOGICAL RESEARCH|
By Dr. WILLIAM HERBERT HOBBS
BUT a few years ago, the American naval officer serving his tour of duty upon the European station found in the antiquated vessels in which he was compelled to appear a constant source of mortification. This condition has now passed, and it is the geologist who in his turn is humiliated as the modern European earthquake station is opened for his inspection. A great earthquake upon American home territory has been registered by all first-class seismographs throughout the world, and the records have been collected for comparison and study at central stations. It is the kindest thing to say of the American records that they are a negligible quantity—for measured by modern standards they are—but unfortunately their inclusion in the autograph albums of the California earthquake of 1906 does not allow them to be overlooked. Thus the backwardness of our country in a most important branch of the great science, in which we had perhaps thought ourselves entitled to some respect, is patent to all.
It will hardly be claimed for us that the United States offers no opportunity for earthquake investigation. In 1811 a devastating quake affected a large area in the central Mississippi Valley, in 1872 occurred the great Owens Valley earthquake in Nevada, and in 1887 the Sonora earthquake of even greater violence; not to mention the Charleston and the recent California seistus. Lighter shocks have been frequent, and the greatest of earthquake authorities, the Count de Montessus de Ballore, showed some years ago that New England, the St. Lawrence Valley, the central Atlantic coast generally, the central Mississippi Valley, and above all the Pacific coast of the United States, must be regarded as notable earthquake provinces.
The better to understand our true position, let us consider what has been accomplished in earthquake investigation within the last ten years. First, and most important, the laws of earthquake distribution have been determined, and the relation of earthquakes to topography and geology has given us a new branch of science—seismic geography. This is almost exclusively the work of one man, the Count de Montessus de Ballore, major of artillery in the French army, who has given the better part of his life to this arduous labor.
From a wholly different direction the problems of earthquakes have been approached through the perfecting of seismometrographs, until they register all great seisms of our planet, however distant. This point reached, an entirely new field has been opened before our eyes. The new autographs of earthquakes have characters dependent upon the distances the waves have traveled to produce the record; so that the observer at a station can unaided give the distance of the disturbance within 50 miles, an error negligible in view of the extended area disturbed.
By combining records made at several widely-separated stations, not only the distance from a given station, but a sufficiently exact location for each quake, is easily obtained. To have developed a great system of some forty such stations, scattered throughout the length and breadth of the globe, is the great service rendered to science by the British Association for the Advancement of Science, especially, and by the leader of its Seismological Committee, Professor John Milne. Thus it has been revealed that the great earthquakes of the planet are twenty-fold more numerous than those reported by observation in situ, and that most of them occur upon the floor of the ocean, where other methods of observation would have failed to reveal their presence.
The analysis of the complex of waves registered in the seismogram is extending our knowledge of the nature of the earth's interior, and affording the solution of problems which, in importance and in difficulty of approach from other directions, can only be compared with those now being solved by the study of radioactivity.
No attempt to sum up the achievements of seismological research during the past ten years should fail to note the fact that the Japanese have for systematic and thorough study of the general problems, but even more for the practical applications of these investigations to the amelioration of the conditions in an earthquake-tormented country, taken the first place among the nations. Italy, also, with almost a score of stations of the first rank and with two hundred correspondents scattered throughout its small territory (to telegraph the first news of a quaking to the main office at Rome), has played no mean part in the advance of the science.
The center of earthquake investigation upon the continent is now, however, the Imperial German Chief Station for Earthquake Investigation at Strasburg. Professor Gerland, its director, now issues the annual catalogue of earthquakes, and he has the credit of having organized, in 1903, the International Seismological Association, and of having founded its journal, the Beiträge zur Geophysik. The work of the station now devolves largely upon his highly-trained assistants, Professor Rudolph and Dr. Sieberg.
The writer assumes that a beneficent result may be expected to follow from the frightful calamity at San Francisco in the stimulation of seismological research in America; so that we may later take our proper share of both the labor and its rewards. The start can easily be made too hastily. There is much contention over the merits of the different types of seismometrograph, which differ as widely as possible. It is perhaps not strange, in view of the new vistas opened for discovery, that the analysis of the records from some instruments not provided with compensating devices has brought out waves supposed to originate in the earth, which exist only in the vibration periods of the instruments themselves.
America's broad extent and her outlying territories and protectorates (Alaska, Cuba, Porto Rico, Panama, the Philippines, Hawaii, Guam and Tutuila), offer her special advantages for a correlated system of earthquake stations; but she will do well to wait until her principal station has been well established, her type of seismograph determined, and a corps of trained expert observers found. This will require some time, and can be greatly hastened if pride be put aside and some one of the thoroughly trained men available in Europe be invited to superintend the erection of the first earthquake station.
Some sacrifice the pioneer must always make, and so it happens that the English stations are fitted out with a type of instruments already obsolescent. On the point of establishing her outlying stations (German East Africa, Shan Tung, Samoa), Germany will be more fortunate. The maker of scientific instruments for almost the entire world, she has steadily perfected her types before launching upon the larger undertaking. America will have at least the consolation of profiting by the experience of the other nations during the past ten years, and there is need for much study of it.
The recent investigation of earthquakes has thus developed along two somewhat different lines: (1) the macroscopic study upon the ground of felt quakes, undertaken by men trained as geologists; and (2) the microscopic investigation of the distant, large, locally 'unfelt' quakes, undertaken at special earthquake stations by men trained as physicists. There is much need that these different lines of endeavor should be brought into as close a union as possible, for only through mutual support can the best results be achieved. As Dr. Sieberg, the secretary of the Strasburg station, told the writer, the more difficult of the seismograms afford equivocal data if not checked by the reports 'from the field.'
The American Association for the Advancement of Science brings the geologist into association with his brother the physicist, as well as with many other scientists who take an interest in investigations of such general interest as those upon earthquakes. The writer takes this opportunity to urge that the association follow the glorious example of its British cousin and select from its membership a committee to watch over the interests of seismological research in America and to direct the course of legislation in accordance with its teachings.