results from MARCONI multichannel seismic data

results from MARCONI multichannel seismic data

S
0
S
Reading of SEG-D and transform to SEG-Y
Resample to 8 ms
Edit and install geometry
4
Spherical divergence correction (average velocity function)
magnification 1
6
Brute stack, constant velocity
8
Velocity analysis
NMO correction
10
magnification 1
Stack
Mixing of traces: 1:3:5:7:5:3:1
12
Stolt migration
AGC for plotting (2000 ms)
14
25 km
0
MARCONI L-5
4
TWT (sec)
J. A. Pulgar(1), J. Gallart(2), G. Fernández-Viejo(1), J. Gallastegui(1), B. Benjumea(3), R. Bartolomé(4), M Ruiz(2), F. Fernández-Baniela(1), O. Ferrer(3)
and the MARCONI Team*
(1) Department of Geology, University of Oviedo, (2) Institute of Earth Sciences, CSIC Barcelona, (3) Department of Geodynamics and Geophysics, University of Barcelona, (4) IFP, Paris
* The MARCONI Team is composed by the following institutions and members: Institute of Earth Sciences-CSIC Barcelone: Josep Gallart, Jordi Díaz, Mario Ruíz, Martin Schimmel, Oriol Gaspà, Eduard Rubio; Dep. Geology, Univ. of Oviedo:
Javier A. Pulgar, Jorge Gallastegui, Gabriela Fernández-Viejo, David Pedreira, Carlos López, Juan Manuel González-Cortina, Fabiola Fernández-Baniela; Dep. Geodynamics and Geophysics, Univ. Barcelone: Josep A. Muñoz, Eduard
Roca, Beatriz Benjumea, Oriol Ferrer, Ylenia Almar; Institute of Marine Sciences-CSIC Barcelone: Belén Alonso, Gemma Ercilla, David Casas, Ferrán Estrada, Marcelí Farran; IEO: Juan Acosta, Pedro Herranz; IGME: Adolfo Maestro,
Antonio Barnolas; SHESA: Magdalena Vicente; IFP: Rafael Bartolomé.
6
Neogene
8
Eocene-Oligocene
magnification 2
?
10
Mesozoic-Paleocene
12
MOHO
Basement
14
0°
-5°
Band-pass filter
CDP sorting (CDP spacing: 12.5 m)
2
-10°
N
Initial processing sequence applied to MARCONI data
2
TWT (sec)
Structure and tectonic
evolutioN of the Cantabrian Margin
of the Bay of Biscay: results from
MARCONI multichannel seismic data
N
0
Undifferentiated MesoTe r t i a r y
Va r i s c a n
thrust
0
00
-4
-4
0
00
Alpine
thrust
4
M0
M34
L-4
M0
-40
00
-200
0
North Iberian Margin
354˚
L-2W
n
-3
0
00
0
-500
n
-100
n
n
n
n
n
n
n
n
n
n
Oviedo
Boundary between N and S
vergent structures
L-5
-300
0
Ebr
o
Bas
i
n
-30
00
ra
nt
Ce
L-6
4
Barcelona
Duero
Basin
em
st
y
lS
L-4
2
-3
00
0
Burgos
45˚
ESCIN-4
MARCONI L-11
Basque-Cantabrian Basin
Zaragoza
IAM-10
BAY OF BISCAY
0
s
ESCIN-2
M0
25 km
Pau
Ibe
rian
Ch
ai
n
Madrid
M
40°
E
A
RR A
E
T E
DI S
A
NE
L-7
L-3
00
-20
Vigo
IAM-11
14
ECORS-Pyrenees
L-2E
L-11
Aquitaine Basin
Pyrenee
00
-20
ESCIN-1
Cantabrian Mts.
León
Bilbao
Santander
L-1
North Pyrenean Zone
00
-30
nn
n
n
n
n
n
n
-200
359˚
South Pyrenean Zone
ECORS -Arzacq
0
u
358˚
46˚
10
SPAIN
L-7
L-10
357˚
-10
00
00
-2
0
A Coruña
n
L-9
0
356˚
-4000
L-8
N
L-9
6
-40
00
-300
0
-300
355˚
ECORS - Bay of Biscay
12
-20
00
-3
CIN
ES
n
0
-20
-4
00
0
353˚
8
FRANCE
TWT (sec)
-5000
00
-10
-5000
0
6
L-8
-4000
-4
00
-10
00
L-3
L-6
TWT (sec)
ESCIN-4
L-11
ECORS-Bay of
Biscay
L-1
-4000
45°
magnification 2
Paleozoic
0
0
-20
IAM-12
-40
0
0
-300
INTRODUCTION
The Bay of Biscay formed during the Cretaceous as a consequence
of the opening of the North Atlantic. The newly formed Cantabrian
Margin remained stable until the beginnning of Tertiary convergence
between the Iberian and Eurasian plates, which led to the building
of the Pyrenean-Cantabrian Mountains on land, and the partial
closure of the Bay of Biscay. The main part of the shortening and
deformation concentrated in the North Iberian Margin. Convergence
stopped at an early stage, making this area a unique place to study
the initial stages of deformation in a passive margin.
South Pyrenean Zone
Normal
fault
STUDIED
AREA
magnification 3
North Pyrenean Zone
0
-200
-40
00
-10
00
N
2
Te r t i a r y B a s i n s
-3000
B AY O F
B I S C AY
S
8
Landes High
-2000
L-2W
10
-10
FRANCE
44˚
00
Refraction profiles (1992-97)
MARCONI PROJECT
Oceanic magnetic anomalies
MOHO
12
Shotpoints (1992-97)
Reflection profiles
ODP/DSDP sites
OBS
Land seismic stations (1993)
Land seismic stations
Reflection profiles ESCIN - IAM
(1991-93)
?
OVIEDO
14
Other seismic profiles
L-2E
L-10
?
BILBAO
SAN SEBASTIAN
0
S
N
Cantabrian
Mountains
2
354˚
355˚
356˚
357˚
358˚
359˚
46˚
ECORS - Bay of Biscay
L-1
BAY OF BISCAY
Type
Air-guns Bolt
Sampling rate
4 ms
1800
Volume
1935-2690 ci
Recording Length
18 s
Depth
8m
Format
SEG-D
Shot interval
40 s
Pre-amp Gain
24 dB
1600
1
1000
2400
2457
800
40
40
0
1600
0
2200
60
400
2000
1800
800
1600
L-9
1400
1200
1000
800
600
400
200
0
-4000
1-L8
DEEP SEISMIC REFLECTION PROFILES
8
Navigation
25 m
Type
GPS, differential
12
Streamer length
2400 m
R/V HESPERIDES
14
Group lenght
25 m
Depth
10 m
25 km
0
-40
00
MARCONI L-6
0
20
800
600
0
20
600
1
4
1-L3
L-2E
BILBAO
SAN SEBASTIAN
Cantabrian
Mountains
43˚
Pyrenees
VITORIA
0
100 km
SPAIN
During summer 2003, 11 deep seismic reflection profiles were acquired in the
MARCONI seismic experiment, aboard the Spanish R.V. Hespérides. They provide a
new 3D image of the structure at the south-easternmost part of the Bay of Biscay. The
project also included the recording of the signal in 24 OBS and OBH and in 46 land
stations.
Preliminary results and interpretations of selected reflection profiles are presented
here (Lines 5, 6 and 11).
TWT (sec)
1591
1400
1000
800
1200
-
1129
1-L10
200
400
600
200
282 282
L-10
1764
OVIEDO
1000
1600
2368
FRANCE
44˚
200
200
1400
1275
1200
2200
800
1000
800
600
400
200
1200
Landes High
400
2000
1-L2W
L-2W
L-7
400
1000
Some remarkable Mesozoic basins were imaged below Tertiary
sediments.They show features related to three main tectonic rifting
event: (1) normal faults and asymmetric basins from the Late JurassicEarly Cretaceous rifting stage; (2) Upper Albian-Lower Eocene
sediments deposited under stable conditions during the passive
margin stage; and (3) inversion structures related to Eocene-Miocene
compression.
2
1-
L9
-300
0
600
1800
-2000
-10
00
The preliminary interpretation of this set of reflection seismic
data shows that the structure of this margin is characterized by a
thick sequence of Tertiary sediments (up to 3 sec TWT) partially
deformed by northward vergent thrusts and related folds. The
kinematic analysis of growth structures in the syntectonic Tertiary
units allows the detailed establishment of the tectonic evolution
of the margin.
10
Number of groups 96
200
80
0
400
600
200
1000
Receiver
Group interval
-10
00
1
10 034
00
1226
1200
800
1000
1200
1400
1600
1800
1200
400
1400
100 km
SPAIN
6
00
1200
L-3
-20
2000
2200
L-6
1000
00
-30
2400
45˚
1400
ESCIN-4
200
63
5
0
800
1-L5
600
Recording
1928
600
L-8
Acquisition parameters for the normal-incidence seismic data
Source
L-11
400
L-4
magnification 3
Pyrenees
1-L1
200
L-5
VITORIA
4
TWT (sec)
353˚
43˚
6
8
10
12
?
MOHO
Another relevant feature inferred from the seismic images is the
development of very recent episodes of deformation affecting the
sea floor, which in some places could be partially related to salt
activity.
CONCLUSIONS
The overall crustal structure of the south-easternmost part of the Bay of Biscay has been interpreted
as a thinned continental crust underthrusted to the S below the extremely steep North Spanish
continental slope. The new MARCONI multichannel seismic images together with the coincident
refraction/wide angle reflection data acquired during the cruise might give more support to this
interpretation and reveal the transition of the North-Pyrenean structural units towards the eastern
part of the Bay of Biscay.
RELATED REFERENCES
Ayarza, P., Catalán, J.R.M., Alvarez-Marrón, J., Zeyen, H.& Juhlin, C. (2004). Geophysical constraints on the deep structure of a limited
ocean-continent subduction zone at the North Iberian Margin. Tectonics, 23 (1), 10.1029/2002TC001487
Fernández viejo, G., Gallart, J., Pulgar, J.A., Gallastegui, J., Córdoba, D. & Dañobeitia, J.J. (1998). Crustal transition between continental
and oceanic domains along the North Iberian Margin from wide-angle seismic and gravity data. Geophys. Res. Lett., 25(23):
4249-4252.
Gallastegui, J., Pulgar, J.A. &Gallart, J. (2002). Initiation of an active margin at the North Iberian continent-ocean transition.
Tectonics, 21(4), 10.1029/2001TC901046.
Pulgar, J.A., Gallart, J., Fernández-Viejo, G., Pérez-Estaún, A., Álvarez-Marrón, J. and ESCIN Group. (1996). Seismic Image of the
Cantabrian Mountains in the western extension of the Pyrenees from in tegrated ESCIN reflection and refraction data.
Tectonophysics, 264, 1-20.
http://www.geol.uniovi.es/Investigacion/Marconi/index.html
14
Mt. Tremblant - Canada - 2004