EARTHQUAKE-ROTATED HEADSTONES AS A MEANS OF RE-EVALUATING EPICENTRAL LOCATION FOR THE 1944 MASSENA-CORNWALL EARTHQUAKE

The Massena-Cornwall earthquake (September 5^th, 1944) is the largest earthquake in New York State history and is still shrouded in considerable mystery; occurring before major advances in seismic-array technology. Two epicenters have been proposed (Milne, 1949; Dewey and Gordon, 1984); however, they are separated by 15 km, an error that could associate each epicenter with entirely different faults. Due to the lack of standardized seismic-array data, there is value in approaching this event from an unconventional data set. 154 earthquake-rotated headstones from 15 cemeteries (US and Canadian) within 20 miles of Massena, NY were measured for original strike and angle of rotation. Strike was measured from the long side of rectangular stones and rotation angles measured with a digital goniometer (0.1° resolution). Using Stereonet 8 and EZ-ROSE software, circular statistics were subjected to Rayleigh, Watson, and Kuiper’s tests, which reveal the data to be non-uniform and unimodal (99% confidence). The mean angle of rotation is 1.9° (cf., 0.1° for unaffected, post-1944 headstones), independent of two-dimensional rotation direction. A significant difference exists between the mean rotation of the post-1944 headstones and the earthquake-rotated headstones (p<0.0001). The methodology of MacDonald and Wentworth (1952) was executed through ArcMap 10.5.1 to yield an area most likely to contain the epicenter. Factoring in the average strike of headstones in each cemetery, an octant was projected based on whether the cemetery had experienced clockwise or counter-clockwise rotation. The area of densest overlap between the projected octants (4 of 5 cemeteries) is an ~20km² area centered in the St. Lawrence River (proposed epicenter at N45.014, W74.815) six miles east of Massena. This area is bisected by the Gloucester Fault; an extension of the of the Ottawa-Bonnechere Graben. This project is an improvement on previous studies of the 1944-rotated headstones (e.g., Berkey, 1945) by analyzing quantitative rotational data within an ArcMap framework. These refined data allow us to propose a new epicenter for the 1944 Massena-Cornwall earthquake, which likely resulted from a rupture along an extension of the Gloucester Fault—a potential threat to the nearby Moses-Saunders Power Dam.