Patrick Smith Academic History PhD Project Title: Combining magma flow modelling and seismicity on Montserrat Supervisor: Prof. Jürgen Neuberg (aka Locko) Funded by NERC Quota Award B.Sc. Natural Sciences from The University of Durham ( ) M.Res. Physics of the Earth and Atmosphere from The University of Leeds (2005/6)

Low frequency seismicity Weak high frequency onset Coda: harmonic, slowly decaying low frequencies (1-5 Hz) → Are a result of interface waves originating at the boundary between solid rock and fluid magma What are low-frequency earthquakes? Specific to volcanic environments

Source Propagation of seismic energy Conduit Resonance Energy travels as interface waves along conduit walls at velocity controlled by magma properties Top and bottom of the conduit act as reflectors and secondary sources of seismic waves Fundamentally different process from harmonic standing waves in the conduit Trigger Mechanism = Brittle Failure of Melt

Propagation of seismic energy

P-wave S-wave Propagation of seismic energy

Interface waves P-wave S-wave Propagation of seismic energy

Interface waves Propagation of seismic energy

Interface waves Propagation of seismic energy

Interface waves Propagation of seismic energy

Interface waves Propagation of seismic energy

reflections Propagation of seismic energy

reflections Propagation of seismic energy

Low frequencies High frequencies FAST MODE: I1 NORMAL DISPERSION SLOW MODE: I2 INVERSE DISPERSION Low frequencies High frequencies Acoustic velocity of fluid Propagation of seismic energy

I1 I2 Propagation of seismic energy

I1 I2 S Propagation of seismic energy

S I1 I2 Propagation of seismic energy

S I1 I2 Propagation of seismic energy

‘Secondary source’ I2 Propagation of seismic energy

Surface-wave ‘Secondary source’ Propagation of seismic energy

Surface-wave Propagation of seismic energy

I1R1 Propagation of seismic energy

I1R1 Propagation of seismic energy

I2 I1R1 Propagation of seismic energy

I2 ‘Secondary source’ Propagation of seismic energy

‘Secondary source’ Propagation of seismic energy

Most of energy stays within the conduit Propagation of seismic energy

Most of energy stays within the conduit Propagation of seismic energy

Most of energy stays within the conduit Propagation of seismic energy

Most of energy stays within the conduit Propagation of seismic energy

R2 Propagation of seismic energy

R2 Events are recorded by seismometers as surface waves Propagation of seismic energy

Why are low frequency earthquakes important? Have preceded several major eruptions in the past Provide direct link between surface observations and internal magma processes Correlated with the deformation and tilt - implies a close relationship with pressurisation processes (Green & Neuberg, 2006)

Incorporating flow model data Motivation for PhD Project Properties of the magma seismic signals (surface) Magma properties (internal) Seismic parameters Signal characteristics Incorporate flow model data into wavefield models Combining magma flow modelling and seismicity on Montserrat

Incorporating flow model data Aims & Methodology Derive seismic parameters Flow model data 2-D Finite-Element Use in wavefield models 2-D Finite-Difference