Part II: The new Malargüe seismic
array
Elmer Ruigrok, Deyan Draganov and Kees Wapenaar
IS@AO Workshop, Cambridge, April 19th 2011
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
Outline
• Why a seismic array in Malargüe?
• 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
Ocean waves
Oceanic -> seismic waves
Seismic arrays (Koper et al., 2010)
Beamforming seismic
waves -> sea state
MalaRRgue, aim 1: monitoring the southern
oceans
Peteroa volcano
Volcano activity, September 2010
MalaRRgue, aim 2: imaging and monitoring the Peteroa
volcano
Tectonic setting
Volcanism features
Imaging challenges still to be addressed
(Gilbert et al., 2006)
• Known
Malargüe
– 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
Regional seismicity
Malargüe
MalaRRgue, aim 4: localizing local seismic activity
Preliminary array design
Positioning with Pierre Auger stations
PA particle detector
Seismic station
• Why a seismic array in Malargüe?
• How will we achieve high-resolution
subsurface images?
Illumination for passive seismology I
A method using teleseismic arrivals
Illumination for passive seismology II
A method using teleseismic arrivals
Crust and upper
mantle
Conventional method: receiver function
Crust and upper
mantle
Receiver function image
Malargüe
New method: seismic interferometry, input
~3km
Crust and upper
mantle
Example response selection
P and reverberations
PP and reverberations
Time-window and separate pre-processing
New method: seismic interferometry, output
Subsurface reflectivity
image (example)
Further processing
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?
?