Preliminary Obtained Data from Borehole Geodetic Measurements in Marmara Region, Turkey
Abstract:Dense continuous GPS networks quantify the time-dependent deformation field of the earthquake cycle. However the strainmeters can capture signals with superior precision at local spatial scales, in particular in the short-period, from minutes to a month. Many relatively small-scale events (e.i. SSEs, creeps) have been successfully determined on the subduction zones. Istanbul located near the most active parts of the North Anatolian Fault (NAF) has been monitored by different observing techniques such as seismic networks and continuous/survey-mode GPS networks for decades. However, it is still essential to observe deformation in a broad range of temporal and spatial scales (from seismology to geodesy and to geology). Borehole strainmeters are very sensitive to deformation in the range of less than a month.
In this study, we present a new project, financially and technically supported by Istanbul Development Agency (ISTKA) and UNAVCO, respectively, which includes the installation of two borehole strainmeters are being deployed in European side of Istanbul in Marmara Region. Since these instruments can also respond to non-tectonic processes, it is necessary to have more instruments to increase spatial coherence and to have additional sensors to detect and model noise (such as barometric pressure, tides, or precipitation). The introduced monitoring system will provide significant insight about the creeping phenomenon and the possible SSE to our understanding of seismic hazards in active zones and possible precursors. Our long term objective is to build a borehole monitoring system in the region. By integrating various data obtained from borehole observations, we expect to get a better understanding of dynamics in the western NAF. In this presentation, we introduce data and ongoing analysis obtained with strainmeters.