1. School of Oceanography, University of Washington, Seattle, Washington 98195-7940 , USA
2. PMEL NOAA and Oregon State University , Newport, Oregon 97365, USA
3. Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
4. Department of Oceanography, University of Hawaii, Honolulu, Hawaii 96822, USA
5. COAS, Oregon State University, Corvallis, Oregon 97331, USA

Correspondence to: H. Paul Johnson¹ Correspondence and requests for materials should be addressed to H.P.J. (e-mail: Email: johnson@ocean.washington.edu).

Abstract

Hydrothermal vents on mid-ocean ridges of the northeast Pacific Ocean are known to respond to seismic disturbances, with observed changes in vent temperature^{1, 2, 3, 4}. But these disturbances resulted from submarine volcanic activity; until now, there have been no observations of the response of a vent system to non-magmatic, tectonic events. Here we report measurements of hydrothermal vent temperature from several vents on the Juan de Fuca ridge in June 1999, before, during and after an earthquake swarm of apparent tectonic origin. Vent fluid temperatures began to rise 4–11 days after the first earthquake. Following this initial increase, the vent temperatures oscillated for about a month before settling down to higher values. We also observed a tenfold increase in fluid output from the hydrothermal system over a period of at least 80 days, extending along the entire ridge segment. Such a large, segment-wide thermal response to relatively modest tectonic activity is surprising, and raises questions about the sources of excess heat and fluid, and the possible effect on vent biological communities.