MODELING SEICHES ON THE DELAWARE AND HOUSATONIC RIVERS PRODUCED BY DIFFERENT MAGNITUDE EARTHQUAKES

The August 10, 1884 New York City earthquake was accompanied by reports of water waves on the Delaware and Housatonic Rivers. These reports indicate the 1884 earthquake generated seiches in these two water bodies. Although not estimated by the observers, the reports suggest that the seiche wave amplitudes may have been about 0.2-0.5 m. The 1884 earthquake has been estimated to be M_Lg5.25 and is largest known event to date to have occurred in the greater New York City area. In this study, we investigate earthquakes ranging from M_Lg5-M_Lg6, and their ability to produce seiches on the Delaware and Housatonic Rivers from an epicenter beneath New York City. We utilize a modeling equation that describes changes to the water surface level of an infinitely long channel in response to a horizontal ground acceleration. With this model we estimate the amplitudes, wavelengths, periods and durations of seiches on the Delaware and Housatonic Rivers due to possible horizontal ground accelerations generated by the 1884 earthquake and by somewhat larger earthquakes at the same epicenter. Scaled observed horizontal ground acceleration records from eastern North America are used as the input accelerations in our modeling. Our results show that moderate magnitude earthquakes centered at New York City can cause seiches of the amplitudes and durations on the Delaware and Housatonic Rivers estimated from the 1884 observations. This study suggests that significant water column and sediment disturbances can take place in nearby rivers and lakes as a result of M_Lg5-M_Lg6 earthquakes in central and eastern North America.