Analogue modelling of Ancestral Mount Bao

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Analogue modelling of Ancestral Mount Bao

• A.M.F. Lagmay
• National Institute of Geological Sciences

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Introduction

• - Ancestral Mount Bao (AMB)
• - North-Central Leyte, Philippines
• Site of the Tongonan Geothermal Power Plant

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Introduction

• AMB is an eroded stratovolcano
• - Traversed and offset by the left-lateral
  Philippine fault
• - Minimum age of 34,000 yrs.

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Introduction

• understand the deformation characteristics
  (structural anatomy) of the AMB
• utility for geothermal exploration
• hazards assessment and prediction

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Methodology

• comparison of analogue sand cone models with the
  natural prototype (AMB)
• surface deformation
• fault analysis

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Methodology

• - analogue sand cone model set-up

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Results

• surface sigmoid
• cone elongation
• summit graben
• normal faults
• reverse faults
• oblique-slip movement of reverse and normal
  faults

• strong erosion on flanks of AMB above the
  strike-slip fault
• landslide deposits on flanks of AMB above the
  strike-slip fault

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Surface sigmoidAnalogue
Natural example
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Cone elongationAnalogue
Natural example
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Summit grabenAnalogue
Natural example
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Summit grabenAnalogue
Natural example
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Normal faults
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Normal faultsAnalogue
Natural example
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Reverse faultsAnalogue
Natural example
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Oblique-slipAnalogue
Natural example
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Strong erosionAnalogue
Natural example
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Landslide depositsAnalogue
Natural example
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Implications

• Geothermal energy
• producing wells tap
• at 2-3 km depth
• fractures control
• permeability
• important to find the
• location of faults/
• fractures at depth

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Implications

• Producing wells in Tongonan straddle the
  Philippine fault on the north-northwest flank of
  AMB
• - Potential in the south-southeast flank of the
  AMB?

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Implications

• - Landslide vulnerability

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Summary
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Acknowledgments

• College of Science Faculty grant
• PNOC-EDC for logistical support and providing
  reference materials
• - UNESCO-IUGG-IGCP project 455