l62 



SCIENCE. 



[Vol. XI. No. 270 



SCIENTIFIC NEWS IN WASHINGTON. 



Mr. Goodfellow's Report : the Locus of the Temblor ; Description of 

 the Great Fault ; Damage to Towns ; the Shaking-up of the Moun- 

 tains ; Fixing the Epicentral Area ; Indications of Two or More 

 Impulses ; the Direction of the Wave ; the Time. — Distortion in 

 Plane-Table Sheets. 



The Sonora Earthquake. 

 Mr. George E. Goodfellow of Tombstone, Arizona, has just 

 sent to Capt. C. E. Dutton, of the United States Geological Survey, 

 a carefully prepared report on the earthquake which occurred May 

 3, 18S7, in the south-western part of the United States and in the 

 northern portion of Mexico. His observations were made during 

 two journeys to the centre of disturbance in Sonora. Very little 

 was learned by the first journey, principally because the time was 

 wasted in searching for an alleged active volcano which had been 

 graphically described by an imaginative correspondent of the New 

 York Herald, but which never existed. 



In a second trip, Mr. Goodfellow met Prof. Jose G. Aguileria, of 

 the Mexican Exploring Commission, which was engaged in making 

 a similar investigation. An arrangement was made with him by 

 Mr. Goodfellow to exchange information ; but, as he had received 

 no report from Professor Aguileria as late as March 5 of the pres- 

 ent year, his report is based almost exclusively upon his own 

 observations. 



After having explained why it was absolutely impossible to ascer- 

 tain the time of the first shock in and about the epicentral area, 

 and some other important data, on account of the absence of time- 

 pieces, the illiteracy of the people and their indisposition to give facts 

 if they had them, the sparse population and inaccessibiUty of the 

 country, the absence of all means of rapid communication or transit, 

 and, last but not least, the unparalleled severity of the rainy season 

 of 1887, Mr. Goodfellow says, — 



" The seismic movements of May 3, 1887, were felt from Toluca, 

 capital of the State of Mexico, 26 leagues south-west from the City 

 of Mexico, to Albuquerque or Santa Fe on the north, and from 

 Yuma and Guaymas on the west, to a point about 60 miles east of 

 El Paso on the east. ... A central tract of maximum intensity, 

 owing to superficial manifestations of ruinous energy, can be located 

 with a considerable degree of certainty, and may be placed in the 

 San Bernardino valley, and probably a contiguous portion of the 

 Teras Mountains. 



" The valley of the San Bernardino is a typical south-western 

 one. It takes its name from an alleged stream, which rises near 

 the border, in the United .States, and, flowing southwards, empties 

 into the Yaqui. These south-western valleys may be divided into 

 three parts, — the narrow bed of the water-course ; the alluvial 

 overflow bottom ; and the mesas, including the foot-hills of the 

 encompassing mountains, for one merges into the other so rapidly, 

 it is hard to tell where the dividing-line may be. Confining my 

 description to the central seismic region, — the Cordilleras of 

 Mexico, — the Sierra Madres, wherein it lies, may be said to have 

 a general north-and-south course. The main chain is composed of 

 numerous short ranges having a trend of 20° north or 30° west. 

 Between each of these ranges is a pass with commonly an easterly 

 and westerly direction, usually carrying more or less water. The 

 valleys before described have the north-and-south direction of the 

 bordering mountains. These mountains, varj'ing in altitude from 

 four thousand to ten thousand feet, are composed, for the most 

 part, of tertiary metamorphic and eruptive rocks. In the range 

 east of the Fronteras valley, and also east of the San Bernardino, 

 are paleozoic strata, presumably carboniferous. The mesas are 

 made up of more or less closely aggregated drift from the moun- 

 tains. The depth of this detritus maybe gauged by a description of 

 some mesas in the neighborhood of Babispe. Between Babispe 

 and the Madera Mountains is a mesa several miles in length which 

 is completely isolated. The level of the river at Babispe is about 

 2,950 feet ; and this mesa rises to the height of 4,500 feet, 1,500 

 feet above the altitude of the river, and is composed entirely of 

 coarse drift. This is shown in many places by channels of lateral 

 erosion. 



" The water-courses display the usual phenomena of south-west- 

 em streams, water appearing in occasional places throughout the 



entire length of the bed, but a great quantity from a few inches to 

 a few feet beneath the surface. On the eastern margin of the San 

 Bernardino valley, where mesas merge into foot-hills, close to the 

 steeper part of the mountains ; on the mesas and in the water- 

 courses of the valley, — are located the evidences of the severity of 

 the earthquake. These consist of a single large fault and many 

 minor fissures and downthrows. The former is on the base of 

 the mountains ; the latter, on the mesas and in the immediate beds 

 of the streams. The large fault begins at the northern end of the 

 valley, a few miles south of the line, in what is called Elias Creek, 

 a tributary of the San Bernardino. It commences very gradually 

 on the southern bank of the stream, increasing in width as it makes 

 a curve towards the canon of Los Embudos, from which point to 

 its end the general direction of the fissure is north and south. 

 It has a winding course, following the tortuous line of the base 

 of the ranges m all its sinuosities to and across the Yaqui River, 

 into the Teras Mountains some miles. Its total length, as far as 

 followed, is about thirty-five miles." In a private letter to Captain 

 Dutton, Mr. Goodfellow says, " In a note to Science, I stated that 

 the fault was one hundred miles in length. This was a great 

 error." He then explains that there are no good maps of Sonora 

 and Chihuahua, save one, and that one he had not seen at the 

 time. He was therefore obliged to judge of the length of the fis- 

 sure by the time it took him to travel, and by very uncertain Mexi- 

 can reports of distances. " The average difference of level between 

 the two sides is a little over seven feet. In some places, as oppo- 

 site Pitaicachi, the difference is much greater. In its entirety north 

 of the Yaqui, it conforms to the usual law of faults by having the 

 hanging wall the lowest ; but, after passing that river some two 

 miles, there is a place for a short distance, some two or three hun- 

 dred yards, where the hanging wall is the highest. The difference 

 in level of the portion south of the river is about three feet. At 

 the point mentioned, where the hanging wall is elevated, the varia- 

 tion is a trifle more. 



" The first question rising in the mind, after viewing the fissure, 

 is, ' Is it an ideal fault, or the mere changing of the drift of the 

 mesas by reason of alteration in subterranean reservoirs of the val- 

 ley ? ' As favoring the first view, is the fact that it lies so near to 

 the base of the mountains its entire length. With the structure of 

 the valleys, before described, did it lie out on the mesas away from 

 the foot of the Sierras, the conclusion would be almost irresistible 

 that it is nothing more than a slip of alluvial drift, as the river-bed 

 downthrows undoubtedly are. But, by examining closely its locale 

 and characteristics, there seems a preponderance of evidence favor- 

 ing the first opinion. Still there is this one thing to be recorded : 

 nowhere in its path, as far as I saw it, can be seen an instance of 

 the solid rock showing a participation in the fissuring, except at 

 Pitaicachi, where a dike may be seen in the breast of the slip. 

 This, I think, is more apparent than real. There are but three 

 places that I saw along the line where such rents could show. 

 These are, first, a small cafion a short distance north of Pitaicachi ; 

 second, a caiion in the Cabellera Mountains ; next, at the Yaqui 

 River. In all of these places is running water, which would have 

 been sufficient to destroy evidence of petrous rupture. In the up- 

 per caiion, which I will call ' Eiisu,' the fissure passes some three 

 hundred feet to the west, and below a stratified mass of shaly rock 

 which rises abruptly at this point. The approaches to these cafions 

 are very steep ; the walls at the locus mentioned being on the 

 southern side almost vertical, on the other at an angle of at least 45°. 

 The causes, then, of partial non-appearance of the crack on the 

 sides of the caiion are self-evident, — the inclination is too great. 

 In every one of the other arroyos and cafions crossed by the fissure, 

 the bottom had as great a rent as the surface of the mesa above, 

 and the walls were depressed proportionately to their inclination. 

 In the Cabellera Caiion the fault is somewhat closer to the rocks, 

 but, aside from this, the other manifestations are the same. I 

 have no doubt that in both, at the time of the first disturbance, the 

 alteration of level in their beds was equal to that on each side 

 above, but the stream soon filled and levelled them. That this is 

 the true solution of the problem, I have had ample evidence in 

 other arroyos usually dry. In these, succeeding the rains and con- 

 sequent temporary torrential flow, the break was rapidly evened, 

 and was no more visible than in the places mentioned. At San 



