58 research outputs found
Generation of a combined dataset of simulated radar and electro-optical imagery
In the world of remote sensing there exist radar sensors and EO/IR sensors, both of which carry with them unique information useful to the imaging community. Radar has the capability of imaging through all types of weather, day or night. EO/IR produces radiance maps and frequently images at much finer resolution than radar. While each of these systems is valuable to imaging, there exists unknown territory in the imaging community as to the value added in combining the best of both these worlds. This work will begin to explore the challenges in simulating a scene in both a radar tool called Xpatch and an EO/IR tool called DIRSIG. The capabilities and limitations inherent to both radar and EO/IR are similar in the image simulation tools, so the work done in a simulated environment will carry over to the real-world environment as well. The synthetic data generated will be compared to existing measured data to demonstrate the validity of the experiment. Future work should explore registration and various types of fusion of the resulting images to demonstrate the synergistic value of the combined images
SKS splitting in Southern Italy: anisotropy variations in a fragmented subduction zone.
In this paper we present a collection of good quality shear wave splitting measurements in Southern Italy. In
addition to a large amount of previous splitting measurements, we present new data from 15 teleseisms recorded from 2003 to 2006 at the 40 stations of the CAT/SCAN temporary network. These new measurements provide additional constraints on the anisotropic behaviour of the study region and better define the fast directions in the southern part of the Apulian Platform. For our analysis we have selected wellrecorded
SKS phases and we have used the method of Silver and Chan to obtain the splitting parameters: the azimuth of the fast polarized shear wave (φ) and delay time (δt). Shear wave splitting results reveal the
presence of a strong seismic anisotropy in the subduction system below the region. Three different geological and geodynamic regions are characterized by different anisotropic parameters. The Calabrian Arc domain has fast directions oriented NNE–SSW and the Southern Apennines domain has fast directions oriented NNW–SSE. This rotation of fast axes, following the arcuate shape of the slab, is marked by a lack of resolved
measurements which occurs at the transition zone between those two domains. The third domain is identified in the Apulian Platform: here fast directions are oriented almost N–S in the northern part and
NNE–SSW to ENE–WSW in the southern one. The large number of splitting parameters evaluated for events coming from different back-azimuth allows us to hypothesize the presence of a depth-dependent anisotropic
structure which should be more complicated than a simple 2 layer model below the Southern Apennines and the Calabrian Arc domains and to constrain at 50 km depth the upper limit of the anisotropic layer, at least at the edge of Southern Apennines and Apulian Platform. We interpret the variability in fast directions as
related to the fragmented subduction system in the mantle of this region. The trench-parallel φ observed in Calabrian Arc and in Southern Apennines has its main source in the asthenospheric flow below the slab likely
due to the pressure induced by the retrograde motion of the slab itself. The pattern of φ in the Apulian Platform does not appear to be the direct result of the rollback motion of the slab, whose influence is limited to about 100 km from the slab. The anisotropy in the Apulian Platform may be related to an asthenospheric
flow deflected by the complicated structure of the Adriatic microplate or may also be explained as frozen-in lithospheric anisotropy
Seismic anisotropy reveals focused mantle flow around the Calabrian slab (Southern Italy)
SKS splitting at the Calabrian subduction zone, with delay times (δt) up to 3s, reveals the presence of a strong anisotropic fabric. Fast directions (ϕ) are oriented NNE-SSW in the Calabrian Arc (C.A.) and rotate NNW-SSE to the north following the arcuate shape of the subducting plate. We interpret the trench-parallel ϕ as local-scale mantle flow driven by the retrograde motion of the slab; the absence of trench perpendicular ϕ below the Southern Apennines (S.A.) excludes the presence of a seismically detectable return flow at its NE edge. This may be due to the relative youth and limited width of the S.A. slab tear. A possible return flow is identified farther north at the boundary of the S.A. and Central Apennines. Different and weaker anisotropy is present below the Apulian Platform (A.P.). This implies that the influence of the slab rollback in the sub-slab mantle is limited to less then 100 km from the slab
Generation of a Combined Dataset of Simulated Radar and EO/IR Imagery
In the world of remote sensing, both radar and EO/IR (electro-optical/infrared) sensors carry with them unique information useful to the imaging community. Radar has the capability of imaging through all types of weather, day or night. EO/IR produces radiance maps and frequently images at much finer resolution than radar. While each of these systems is valuable to imaging, there exists unknown territory in the imaging community as to the value added in combining the best of both these worlds. This work will begin to explore the challenges in simulating a scene in both a radar tool called Xpatch and an EO/IR tool called DIRSIG (Digital Imaging and Remote Sensing Image Generation). The capabilities and limitations inherent to both radar and EO/IR are similar in the image simulation tools, so the work done in a simulated environment will carry over to the real-world environment as well. The goal of this effort is to demonstrate an environment where EO/IR and radar images of common scenes can be simulated. Once demonstrated, this environment would be used to facilitate trade studies of various multi-sensor instrument design and exploitation algorithm concepts. The synthetic data generated will be compared to existing measured data to demonstrate the validity of the experiment
Shear wave splitting in southern tyrrhenian subduction zone (Italy) from CESIS and CAT/SCAN projects
In the years 2003 -2006 several broad band stations were installed in Southern Italy:
15 permanent ones (CESIS project), improved the INGV Italian national network and 40 temporary ones were installed in the frame of CAT/SCAN NSF project.We present shear wave splitting measurements obtained analyzing SKS phases and local S phases
from slab earthquakes. We used the method of Silver & Chan to obtain shear wave splitting parameters: fast direction and delay time. Shear wave splitting measurements reveals strong seismic anisotropy in the mantle beneath Southern Tyrrhenian subduction
system. The SKS splitting results show fast polarization directions varying from NNW-SSE in the Southern Apennines to N-S and to E-SW in Calabria, following the strike of the mountain chain. Moving toward the Adriatic sea the fast directions rotate from N-S to NE-SW. Fast directions could indicate the mantle flow below the slab, due to its retrograde motion but also the lithospheric fabric of the subducting plate. In the Tyrrhenian domain, above the slab, from Sardinia to the Italian and Sicilian
coasts the dominant fast direction is E-W and could be related to the opening of the Tyrrhenian basin and to the corner flow in the asthenospheric wedge. In Sicily fast directions depict a ring around the slab edge supporting the existence of a slab
tear and of a return flow from the back to the front of the slab. Measurements obtained
with intermediate and deep earthquakes slab S phases show an extremely complex pattern of fast directions. They are mostly distributed in front of the Tyrrhenian Calabrian coast in correspondence of the fast velocity anomaly imaged at 150 km depth
by tomography. We can relate this fast directions variability to the complex structure of the slab itself. The complex pattern of SKS and S splitting measurements suggests the presence of local scale mantle flow controled by the motion of an anisotropic slab
SKS splittings in the southern Apennines-Calabrian arc region (southern Italy)
During the years 2003-2006 CAT/SCAN (Calbarian-Apennine-TyrrhenianlSubductionCollision-
Accretion Network) temporary broadband stations operate in Southern Apennine
and Calabria (Italy). In the same period CESIS-INGV project improved the number of
permanent seismic stations in the same area. We analyze the data recorded to study seismic
anisotropy and to investigate the mantle flow in the boun(fary-zoile{ between Southern
Apennine and Calabriaibeneath and above the subducting slab. In the current work we
present new shear wave splittings obtained analyzing SKS phases of 15 teleseisms with
epicentral distance ranging from 88.40 to 98.20 and magnitude greater than 6.0. We used the method of Silver & Chan (1991) to obtained anisotropic parameters: delay time and fast polarization direction. The splitting parameters reveal strong seismic anisotropy in the mantle beneath Southern Tyrrhenian Sea- Calabrian Arc System that seems to be controlled by the slab presence. The clear variability in the fast directions allow us to hypothesize the existence of different anisotropic domains: fast polarization directions vary from NNW -SSE
in the tyrrhenian side ofthe Southern Apennine to N-S and NE-SW toward the Adriatic Sea. Moving toward the Calabria fast directions are prevalently trench parallel showing a NE-SW orientation following the strike on the mountain chain
Integrated SEED data archive for temporary seismic experiments
One of the most valuable results achieved during
the work on S5 project is the implementation of a new temporary
network data management that allows the integration in the
National Data Center together with all other seismological data produced
by INGV. This makes all data gathered during temporary experiments immediately
available from the same source and in the same data format (SEED)
increasing the availability for processing and analysis. Moreover the data are distributed
to the scientific community using the EIDA (European Integrated Data Archive
http://eida.rm.ingv.it/).
The first application has been carried out for the Messina 1908-2008 experiment
(WP2.2) http://dpc-s5.rm.ingv.it/en/Database-MessinaFault.html where has been
achieved the complete integration of permanent networks (National Seismic Network,
MedNet and Peloritani Local Network), temporary deployments (INGV-CNT and INGVCT
mobile networks) and OBS data.
All the procedures were used and further improved during the L'Aquila sequence
(Task 4) where data was available for processing together with permanent
network data as soon as it was gathered from the field giving to the
scientific community the opportunity to study the evolution of the
seismic sequence with higher density of stations (WP4.2)
( h t t p : / / d p c - s 5 . r m . i n g v . i t / e n / D a t a b a s e -
AquilaFaultSystem.html).UnpublishedSede Ispra | Via Curtatone 7, Roma1.1. TTC - Monitoraggio sismico del territorio nazionaleope
Results from the seismological component of CAT/SCAN, the Calabria-Apennine Tyrrhenian/Subduction-Collision-Accretion-Network
The Calabrian Arc is the final remnant of a Western Mediterranean microplate driven by rollback. The Calabrian-Apennine-Tyrrhenian/Subduction-Collision-Accretion Seismic Network (CAT/SCAN) was a passive seismic experiment to study of the Calabrian Arc and its transition to the southern
Apennines. The follow up Calabrian Arc project added a multidisciplinary (seismology, geology, geomorphology,
geochronology, GPS, etc.) approach to better understand the tectonics of southern Italy imaged by the CAT/SCAN experiment. Here we focus on the seismological results of the
two projects.
The CAT/SCAN land deployment consisted of three phases. The initial phase included an array of 39 broadband seismometers onshore, deployed during the winter of 2003/4.
In September 2004, the array was reduced and in April 2005, the array was reduced once again. The field deployment was completed in October 2005. Offshore, 12 broadband Ocean
Bottom Seismometers (OBSs) were deployed in the beginning of October 2004. However, only 1 was recovered normally while several others were recovered after being disturbed by trawling. The experiment goal was to determine the structure of the Calabrian subduction and southern Apennine collision
systems and the structure of the transition from oceanic subduction in Calabria to continental collision in the southern
Apennines.Published7922T. Tettonica attivaN/A or not JCRrestricte
Lateral Changes of seismic anisotropy in the upper mantle around the Northern Apennines
We performed three-dimensional analysis of anisotropic parameters of body waves to develop a 3D self-consistent dynamic model of the syn-convergent extension in the Northern Apennines within the multidisciplinary project RETREAT. Simultaneous extension within the convergent margin can be the consequence of the retreat
of the subducting Adriatic plate from the orogenic front, caused by sub-lithosphere
mantle processes that seismic anisotropy can help to decipher. We use data recorded
by the RETREAT temporary array consisting of 35 stations complemented by data of permanent INGV observatories. Currently, 18-months of data are available from some stations, representing half of the passive experiment duration. We detect many examples of core-refracted shear-wave splitting within the upper mantle, and observe both distinct lateral variations of anisotropic parameters and their dependence on the
direction of propagation. In particular, the fast shear-wave polarization changes from
slab-perpendicular to slab-parallel along the Apennines chain. There is also a distinct
change in the anisotropic signals across the presumed boundary of the Tyrrhenian and
Adriatic micro-plates. Variations of the splitting time delays and orientation of the fast shear waves, together with considerations on the geodynamics of the area, seem to exclude simple sub-lithosphere mantle corner flow as the only source of the observed anisotropy. Alternate models include (1) a frozen-in fabric of different lithosphere domains, and (2) complex mantle flow associated with the Plio-Pleisocene uplift and extension of Tuscany
The subduction structure of the Northern Apennines: results from the RETREAT seismic deployment
The project Retreating-trench, extension, and accretion tectonics, RETREAT, is a multidisciplinary study of the
Northern Apennines (earth.geology.yale.edu/RETREAT/), funded by the United States National Science Foundation
(NSF) in collaboration with the Italian Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the Grant Agency
of the Czech Academy of Sciences (GAAV). The main goal of RETREAT is to develop a self-consistent dynamic
model of syn-convergent extension, using the Northern Apennines as a natural laboratory. In the context of this project
a passive seismological experiment was deployed in the fall of 2003 for a period of three years. RETREAT seismologists
aim to develop a comprehensive understanding of the deep structure beneath the Northern Apennines, with
particular attention on inferring likely patterns of mantle flow. Specific objectives of the project are the crustal and
lithospheric thicknesses, the location and geometry of the Adriatic slab, and the distribution of seismic anisotropy
laterally and vertically in the lithosphere and asthenosphere. The project is collecting teleseismic and regional earthquake
data for 3 years. This contribution describes the RETREAT seismic deployment and reports on key results
from the first year of the deployment. We confirm some prior findings regarding the seismic structure of Central Italy,
but our observations also highlight the complexity of the Northern Apennines subduction system
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