Installation of EarthScope Borehole Strainmeters in Turkey to complement GONAF.
Abstract:Twice in the past 1000 years a sequence of damaging earthquakes has propagated over a period of a few decades along the North Anatolian Fault (NAF) in Turkey towards Istanbul, with the final earthquake in the sequence catastrophically damaging the city. This occurred most recently in 1509, causing 10,000 casualties in a population of about 200,000. The population is now 20 million, the building stock more fragile, and the last earthquake of the current sequence is considered imminent.
Since July 2014, UNAVCO has installed 2 EarthScope borehole geophysical instrument strings, which include Gladwin Tensor strainmeters and passive, short-period 3-component seismometers, into boreholes provided by internationally supported Geophysical Observatory at the North Anatolian Fault (GONAF) and Bogazici University Kandilli Observatory. Funding for instruments and staff participation was provided by NSF. If the project remains on schedule, we anticipate that 4 additional BSM strings will be installed by the fall 2015.
Our joint international project gives an opportunity to enhance the detection capability of a suite of deep seismometers (GONAF) installed near Istanbul and will permit us to image dynamic rupture along the NAF and to monitor and better understand the tectonic processes leading to failure. The tectonic and geodynamic environment of the NAF near Istanbul in many ways resembles the San Andreas Fault setting of San Francisco; these instruments will enhance the ability to monitor ultra-slow process near the probable source zone of the Mw>7 earthquake beneath the Marmara Sea on the NAF
This project has provided UNAVCO an opportunity to gain experience in strainmeters installations outside of North America. The techniques developed to adapt to the challenges of installing borehole strainmeters on islands and other remote locations with limited resources will greatly enhance our ability to install these BSM instruments in similar locations in the future.