Deepwater Wind did not plan for earthquakes
Credit: Thursday, June 20, 2013 | www.independentri.com ~~
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The proposed wind turbine farm adjacent to Block Island brings up an issue that has probably not been addressed by the developers. The issue is not addressed in most Rhode Island building codes and affects all major Rhode Island structures including buildings, bridges and wind turbines on both land and sea.
The geology of Narragansett Bay is by no means static. Although New England does not have earthquakes often, it has had several major quakes in the past and might well have major quakes in the future. Following are excerpts that show earthquake dates taken from “The History and Future of Narragansett Bay”:
In 1638, a major earthquake rattled Rhode Island and all of New England. Other quakes were felt in 1658, 1727, 1732, 1755, 1783, 1791, 1848, and 1860. In February of 1883, a large earthquake was felt throughout the region, and the epicenter was probably located near Narragansett Bay not far from the proposed site of the new wind turbines located near Block Island. In 1925, a magnitude 7.0 quake rattled New England and Rhode Island, with an epicenter near the St. Lawrence River. An even bigger quake of magnitude 7.2 occurred in 1929 with an offshore epicenter. Other quakes occurred in 1940, 1944, and 1963 in New England, and were felt beside the Narragansett Bay.
Two local quakes centering on or near Narragansett Bay occurred in 1965 and 1967, and both were strong enough to rattle dishes from Bristol to Narragansett. The most recent noticeable earthquake was of magnitude 5.2 and occurred in 1973. Given the average intervals of earthquakes felt beside Narragansett Bay, it should be time for another one quite soon.
Although small quakes have occurred often since 1755, most have not caused any serious damage. This is both good news and bad news. The bad news is the comparative lack of recent serious earthquakes in Rhode Island and New England has led to laxness in building codes and to a general unpreparedness by both state and local governments.
For example, most of the tall buildings in Providence and elsewhere around the Narragansett Bay region are not safe from earthquakes since they were not required to be. Thousands of office buildings and thousands of homes also are at risk from a major regional earthquake. Also at risk are major bridges such as the Verrazzano Bridge between Jamestown and Newport, the Pell Bridge, the Mt. Hope Bridge, and scores of smaller bridges throughout the region.
Even the new tolls on the Sakonnet River Bridge could not pay for the simultaneous collapse of all Rhode Island bridges in a local earthquake of magnitude 8.0 on the Richter scale with an epicenter in Narragansett Bay.
Not only could an earthquake itself cause structural damage, but if the epicenter is located offshore – which is quite likely given the history of earlier earthquakes – it is possible that a tsunami also might occur.
The proposed wind farm near Block Island makes this a good opportunity for Rhode Island to follow the lead of Japan and introduce building codes that will help alleviate earthquake damages. The earthquake in Haiti which destroyed so many buildings and killed thousands measured 7.0 on the Richter scale. By contrast, the recent Japanese earthquake measured 8.9. Since Rhode Island has had earthquakes larger than 7.2 on the Richter scale within the past few hundred years, it would be a good idea to emulate the new building codes in Japan.
In the context of both the new proposed turbine farm and existing wind turbines already located on land in several Rhode Island towns, unless they can withstand earthquakes of more than 7.0 on the Richter scale, they are at considerable risk.
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