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Seismic Network at the Pierre
Auger Observatory
Enrique G. Triep
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Instituto Geofísico-Sismológico Ing. F. S. Volponi (IGSV), Facultad de Ciencias Exactas,
Físicas y Naturales, Universidad Nacional de San Juan
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Instituto Nacional de Prevención Sísmica (INPRES)
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Departamento de Sismología, Facultad de Astronomía y Geofísica, Universidad
Nacional de la Plata (Dep. Sism., UNLP)
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Pierre Auger Observatory
Project BSR (Bloque San Rafael): PICTO Riesgo Sísmico Nº 254
Agencia Nacional de Promoción de Ciencia y Técnica
Pierre Auger Observatory Seismic Stations
Installation started on December/2009 and finished on July/2010
Data transmitted by Internet to IGSV
Stations
LOMA AMARILLA Station
LOMA AMARILLA Sensor
LOMA AMARILLA Digital Recorder and Battery
REF TEK Recorder
Protocols:
TCP: communications
FTP: data transfer
RTP (Real Time
Protocol): monitoring
Other recorders
installed in the network
(SARA and PCN
digitizers) with Linux
system:
access by SSH and
data retrieval by SFTP
LOMA AMARILLA Station
Enlarged BSR Seismic Network
Pierre Auger Observatory Stations since December/2009July/2010 (Data transmitted by internet to IGSV)
Autonomous Stations since December/2010
Autonomous Stations to be installed within 2011
CARAPACHO Station
Autonomous station
SAN PABLO Station
Autonomous station
PAJARO BOBO Station
Autonomous station
We note that in the present project the
larger part of the seismic equipment
belongs to Instituto GeofísicoSismológico Ing. F. S. Volponi (IGSV),
UNSJ, and a smaller part to the
Instituto Nacional de Prevención
Sísmica (INPRES). There are no
borrowed equipment!
Seismic
RegionalNetwork
Seismicity
Pierre Auger Observatory Stations set up from December/2009 to July/2010
(Data transmitted by internet to IGSV)
Crustal earthquakes
Subducted Nazca Plate earthquakes
Las Malvinas-Nevado fault
Regional Seismicity Cross-Section
(km)
(km)
Crustal earthquakes
Subducted Nazca Plate earthquakes
Crustal Seismicity
NEIC Catalog
1977-2010
2001 earthquake,
our determinations
2002 earthquake
NEIC
2003 earthquake
and aftershocks
NEIC
2003 earthquake
CMT
1929 earthquake
Epicenter determined
by P wave travel times
Yellow cross: epicenter
determined according
to damaged
Cities and towns
Beach balls: focal
mechanism diagrams
M≈6.0 May/30/1929 Earthquake
Villa Atuel Town
Adobe Construction
M≈6.0 May/30/1929 Earthquake
Villa Atuel Town
Brick Construction
Thus, the area is seismically active and has
important destructive earthquakes.
What we know from geophysical work up to
now and what would like to know from our
experiment?
Two previous experiments in the region
After Ramos and Kay, 2006
CHARGE seismic stations transect, December/2000-March/2002
Magnetotelluric experiment, 2007
Our seismic network area, December 2009-December 2013
Chile Argentina Geophysical Experiment (CHARGE)
Broadband Seismic Network 2000/12-2002/3
-33°
Our BSR network area
Stations LENA and RAFA
did not provided data
Subducted Nazca plate seismicity located by CHARGE
Earthquake magnitude: 3.2 ≤ M ≤ 3.7
Our BSR network area
A
B
A
B
Anderson et al., 2004
Regional P and S wave travel time data were used to obtain 3D seismic
tomography models for Vp, Vs and Vp/Vs
Our BSR network
area where
tomography will be
performed
We hope to solve
upper mantle and
crust tomography
Wagner et al., 2005
Stacked S Receiver Functions
We aim to determine 3D Moho
morphology (not only in one
cross-section as in this case)
using converted P to S waves,
receiver functions, etc.
Heit et al., 2008
Heit et al., 2008
Seismic Anisotropy below the subducted Nazca plate
Using SKS and SKKS waves
Our BSR network area
Interpretation (considering fast
seismic directions same as the
mantle flow):
South of 33º S, mantle flow is
parallel to the trench.
North of 33º S, mantle flow tend
to be perpendicular to trench.
That is, the flow escape to the
East under the flat slab.
Anderson et al., 2004
We will work with SKS and SKKS
waves to determine upper mantle
seismic anisotropy below the
Nazca plate, and with S waves
from local earthquakes for the
upper mantle above the plate
Magnetotelluric (MT) 2D preliminary data analysis at 34º S, below the Payún Matru
Volcanic Field, suggest a “tentative identification” of a conductive mantle plume from
200 km depth to at least 40 km below the surface (Burd et al., 2008)
Warning:
Do not thrust the details of
this structure at this time!
Only consider that a narrow,
near vertical conductive
structure must connect the
shallow to deep mantle
We will look for features
like this in our
experiment region
using tomography and
seismic anisotropy
Next: Some examples of seismograms
from our BSR network
Local Earthquake recorded at LOS LEONES Station
Vertical and horizontal components show clear P and S wave arrivals
Mw=8.8 Chile Earthquake, February/27/2010 as was recorded in LOS LEONES station.
The digital recorder did not have enough “Gain” and the signal was saturated.
The gradual signal onset is a common characteristic of the Chile earthquakes when they
are recorded in western Argentina.
Mw=8.8 Chile Earthquake, February/27/2010, as was recorded in
LOS LEONES station after filtered between 1 and 5 Hz
Histogram of S-P wave times from Auger Observatory data in same 40 days
period before and after the Mw=8.8 Chile Earthquake
40 days before
S-P times ~ 10-14sec are from
local earthquakes
40 days after
Note the large increase of local
earthquakes after the great
earthquake
The great earthquake
activated seismic activity in
the Argentine side!
Goals of our project
• Precise Location of the Crust and Nazca
Plate seismicity
• Focal Mechanisms (First P wave motion
and Moment Tensor Inversion)
• Seismic Tomography
• Seismic Anisotropy
• Results correlated with tectonic and
geodynamical features
Some small interdisciplinary collaboration
already done:
Explanation of which was the wave from
Chile Mw=8.8, February 27, 2010,
earthquake that caused the effect on the
water tanks transparence at the Pierre Auger
Observatory
Auger Observatory
Average Background Events Rate versus Time (operation as Geiger mode)
Water transparency decrease during about 70 sec: 24 σ (sigmas!)
Sb
Mw=8.8, 2010, Chile
Earthquake
Epicentral distance to
Los Morados
Fluorescence station:
3.27º
Waves travel time:
Pn 49.91 sec
Pb 57.32 sec
Sn 88.91 sec
Sb 99.30 sec
The more energetic
S waves are the
blameworthy!
99.30 sec
70 sec
Earthquake origen time
Could we see this
type of effects for
smaller nearby
earthquakes?
After Xavier Bertou
Personal comm.
CONCLUSIONS
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The opportunity to install seismic stations at the Pierre Auger
Observatory, taken advantage of its building facilities, internet, power,
and specially the help of its people, have been of an immense platform
from which we were able to start and develop our research project.
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We propose to establish a digital broadband permanent seismic
network at the Pierre Auger Observatory.
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The network operation and supervision should be under the three only
institutions in Argentina that works in seismology: Instituto GeofísicoSismológico Ing. F. S. Volponi (IGSV), UNSJ, Instituto Nacional de
Prevención Sísmica (INPRES), Departamento de Sismología, UNLP.
INPRES is taking care of the National Seismic Network in Argentina,
and has an up to date laboratory and technical expertise to control,
calibrate and repair sensors and data loggers.
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The network should have open data accessibility, and at least one of
the stations should make the data availability in real time.
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Clearly, other geophysical fields would benefit with the infrastructure,
organization, and support of the Pierre Auger Observatory.
THANKS VERY MUCH