| Title | Understanding Fracture Mechanisms in an Evolving Transtensional Stress Regime by Inversion of fault Sets, P-Waves and GPS Measurements Implications to the Development of the Tongonan Geothermal Field |
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| Authors | M.A. Aurelio, J. Punongbayan and T.C. Bacolcol |
| Year | 2006 |
| Conference | PNOC-EDC Geothermal Conference |
| Keywords | |
| Abstract | While tensors calculated from the inversion of fault data sefs provide information on the sfress conditions in the geologic past, the present-day sfress sfafe may be determined from focal mechanism solutions (FMS) derived from the inversion of body waves from microearthquakes as well as from velocity vectors computed from repeated positioning measurements. Combining resulfs from fhese three techniques allow for a continuous sfress record, necessary in reconstructing the evolution of the stress safe in a given area. Stress fensors, FMS and GPS vectors in the Tongonan geothermal field and vicinity indicate that the area has been experiencing alternating or simultaneouse ventso f stike-slip faultinga nd normal faultings ince the establishmenot f the volcanice difice some 3 Myr ago. The principal sfress axrs 6r determined from strike-slip fault populations is generally oriented WSW-ENE while the /easf sfress axis os from normal fault populafions is oriented NWSE, parallel to the strike of the PF, while FMS indicate an easterly and moderately dipping ot and a northerly and flat 6s. These events result from an evolving sfressr egime controlledb y a transtensionasl tep-over segment of the left-lateral Philippine Fault. Understanding the mechanism of fracture sysfems produced by fhis sfress regime has valuable implications in geothermal exploration and development. |