Part II: The new Malargüe seismic array

IS@AO Workshop, Cambridge, April 19th 2011

Elmer Ruigrok, Deyan Draganov and Kees Wapenaar

MalaRRgue

• MalaRRgue: A large seismic array in the Malargüe department

• Partial collocation with Pierre Auger Observatory• 2012: temporary array of 80 stations• >=2013: ‘permanent’ array • Monitoring and imaging the subsurface• Application of recently developed techniques• International team of geophysicists

ICES

• Why a seismic array in Malargüe?

Outline

• How will we achieve high-resolution subsurface images?

• Why a seismic array in Malargüe?

• How will we achieve high-resolution subsurface images?

The missing seismic array …

Swell

Local waves

Oceanic -> seismic waves Beamforming seismic waves -> sea state

Ocean waves Seismic arrays (Koper et al., 2010)

MalaRRgue, aim 1: monitoring the southern oceans

Peteroa volcano

MalaRRgue, aim 2: imaging and monitoring the Peteroa volcano

Volcano activity, September 2010

Tectonic setting

Volcanism features

Imaging challenges still to be addressed

(Gilbert et al., 2006)

Malargüe

• Known– Moho depth

• Our imaging targets– Moho topography– Basin topography– Nazca slab depth– Magma intrusions– Major faults

MalaRRgue, aim 3: detailed imaging of the lithosphere

Local seismicity

MalaRRgue, aim 4: localizing local seismic activity

Malargüe

Regional seismicity

Preliminary array design

Positioning with Pierre Auger stations

Seismic station

PA particle detector

• Why a seismic array in Malargüe?

• How will we achieve high-resolution subsurface images?

A method using teleseismic arrivals

Illumination for passive seismology I

Crust and upper mantle

Illumination for passive seismology II

A method using teleseismic arrivals

Crust and upper mantle

Conventional method: receiver function

Receiver function image

Malargüe

Crust and upper mantle

~3km

New method: seismic interferometry, input

Example response selection

Time-window and separate pre-processing

P and reverberations

PP and reverberations

Further processing

Subsurface reflectivity image (example)

New method: seismic interferometry, output

A dense sensor network

Malargüe

T-array– 2 orthogonal linear subarrays– 3 km inline spacing– 42 stations – ‘Basin’ setting

Illumination by earthquakes and storms

I: Inline earthquakes

II: Inline oceanic storms (Landes et al., 2010)

High-resolution subsurface imaging

1. Reflection imaging instead of conversion imaging

2. Dense sensor network

3. Using not only earthquake responses, but also storm-induced waves

Summary

Large seismic array (80 stations) planned in the Malargüe department

1. Imaging subsurface

2. Monitoring the sea state in the SH

3. Monitoring volcanic activity

4. Monitoring local seismicity

PAO synergies

• Facility and expertise exchange

• Coupling atmospheric gravity waves with seismic waves?

• Coupling lightening to seismic waves?

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