Socorro Earthquake 2 – New Mexico – November 15, 1906

Considerable damage was done to homes but little loss of life, as far as is known. Damage was much more extensive than in the July 16 earthquake because some development had occurred in the intervening months.

An earthquake with a magnitude of at least 7 hit the town of Socorro on November 15, 1906. It was more powerful than the one that had occurred on July 16 of the same year. In the months between July and November there had been a succession of lesser tremors. Any place within 180 miles of Socorro felt the impact of this earthquake. It greatly increased the damage done by the July 16 quake and, in total, represented the most severe shock of the year 1906. Chimneys on the County Courthouse that had been rebuilt after previous damage were thrown down, plaster shaken from walls, upper floors of some two-storey buildings collapsed, and bricks were dislodged from a few houses. Many people in Texas and Arizona remembered the earthquake.

Isoseismals, lines joining places with equal earthquake intensity, are difficult to draw for this earthquake or for its predecessor in July of the same year, because of the limited amount of data available. Nevertheless, it was well known that strong shaking was experienced by people all over New Mexico and in parts of Arizona and Texas. Smaller shocks were observed to be single vibrations backwards and forwards while stronger ones vibrated in different directions. This pattern is usual in strong earthquakes like that experienced in November.

There were also different sounds accompanying the vibrations. The search for the epicenter of this earthquake leads to an examination of the geological history, especially the existence of fault lines. The formation of new fault lines or volcanic eruptions or both of these are the two known causes of earthquakes. The lack of volcanic eruptions and the general character of the shocks suggest that no new fault lines appeared. It seemed likely that the cause of the earthquake was a slip action on an existing fault and its location was on the west side of Socorro.

The evidence for the location of the epicenter is found in the different things that happened. The overthrown chimneys and gables fell to the east. Both the directions taken by falling objects, and the directions in which earth movements occurred were measured in 1906 by hanging pendulums and marking the extent and direction of movement on the floor beneath. These pendulums had to be watched as they moved in response to the earthquake and the length of support as well as the end weight had to be consistent in order to make comparisons over time. The fact that both the July and the November earthquakes were preceded and followed by smaller tremors is consistent with the geological history of this region. Earthquakes have frequently occurred here in clusters over the past few thousand years. One series of earthquakes hit the area between 1898 and 1900. The November 1906 shock was the strongest recorded since 1869.