Automatic Recognition of Landslides Based on Neural Network Analysis of Seismic Signals: An Application to the Monitoring of Stromboli Volcano (Southern Italy)     

Antonietta M. Esposito  Luca D’Auria  Flora Giudicepietro  Rosario Peluso  Marcello Martini 《Pure and Applied Geophysics》2013,170(11):1821-1832

In the last 9 years, the amount and the quality of geophysical and volcanological observations of Stromboli's' activity have undergone a marked increase. This new information highlighted that the landslides on the Sciara del Fuoco flank are tightly linked to the volcanic activity. Actually, at the beginning of the December 28, 2002, effusive eruption, the seismic monitoring network was less dense than now, and therefore it is not known if there was an increase in the landslide rate before the eruption. Despite this, it is known that a big landslide occurred 2 days after the beginning of the eruption which caused a tsunami (December 30, 2002). More recently, the effusive eruption in February 2007 was preceded by an increase in landslides on the Sciara del Fuoco flank, which were recorded by the seismological monitoring system that had been improved after the 2002–2003 crisis. These episodes led us to believe that monitoring the Sciara del Fuoco flank instability is an important topic, and that landslides might be significant short-term precursors of effusive eruptions at the Stromboli volcano. To automatically detect landslide signals, we have developed a specialized neural algorithm. This can distinguish between landslides and the other types of seismic signals usually recorded at the Stromboli volcano (i.e., explosion quakes and volcanic tremor). The discrimination results show an average performance of 98.67 %. According to the experience of the crisis of 2007, to identify changes that can be considered as precursors of effusive eruptions, we set up an automatic decision-making method based on the neural network responses. This method can operate on a continuous data stream. It calculates a landslide percentage index (LPI) that depends on the number of records that are classified by the net as landslides over a given time interval. We tested the method on February 27, 2007, including the beginning of the effusive phase. The index showed an increase as early as at 09:00 UTC on that day and reached its maximum value (100 %) at 12:00, about 40 min before the onset of the eruption. After the beginning of the effusive phase, the index remains high due to the blocks that roll down along the slope from the front of the lava flow. On the basis of these tests, we propose a decision-making method that is able to recognize a trend in the LPI similar to that of 2007 eruption, allowing the identification of precursors of effusive phases at the Stromboli volcano.  相似文献   

Oxygen isotope fractionation between apatite-bound carbonate and water determined from controlled experiments with synthetic apatites precipitated at 10-37 °C     

Christophe Lécuyer  Vincent Balter  François Fourel  Romain Amiot  Olga Otero  Gérard Panczer  Rossana Martini 《Geochimica et cosmochimica acta》2010,74(7):2072-584

The oxygen isotope fractionation between the structural carbonate of inorganically precipitated hydroxyapatite (HAP) and water was determined in the range 10-37 °C. Values of 1000 ln α() are linearly correlated with inverse temperature (K) according to the following equation: 1000 ln α() = 25.19 (±0.53)·T⁻¹ − 56.47 (±1.81) (R² = 0.998). This fractionation equation has a slightly steeper slope than those already established between calcite and water ( [O’Neil et al., 1969] and [Kim and O’Neil, 1997]) even though measured fractionations are of comparable amplitude in the temperature range of these experimental studies. It is consequently observed that the oxygen isotope fractionation between apatite carbonate and phosphate increases from about 7.5‰ up to 9.1‰ with decreasing temperature from 37 °C to 10 °C. A compilation of δ¹⁸O values of both phosphate and carbonate from modern mammal teeth and bones confirms that both variables are linearly correlated, despite a significant scattering up to 3.5‰, with a slope close to 1 and an intercept corresponding to a 1000 ln α() value of 8.1‰. This apparent fractionation factor is slightly higher or close to the fractionation factor expected to be in the range 7-8‰ at the body temperature of mammals.  相似文献   

Seismic stratigraphy of the Miocene–Pleistocene sedimentary basins of the Northern Tyrrhenian Sea and western Tuscany (Italy)     

Pascucci  Merlini  & Martini 《Basin Research》1999,11(4):337-356

Seismic and stratigraphic data of the inland Volterra Basin and of the Tuscan Shelf (Northern Tyrrhenian Sea) have been analysed to determine the tectono-sedimentary evolution of this part of the Northern Apennines from the early Miocene (about 20 Ma) to the present. The area is a good example for better understanding the evolution of postcollisional related basins. The study area is characterized by a series of sedimentary basins separated by tectonic ridges. Similar environmental conditions existed both onshore and offshore as indicated by the occurrence of similar seismic units. The units are separated by major unconformities. The cross-sectional geometries of the deposits of these basins, as defined through seismic reflection profiles, change in a quasi-regular manner through time and space. Early stages (late Burdigalian to early Tortonian) of evolution of the basins are marked by either flat-lying deposits, quasi-uniform in thickness, probably remnants of originally wider and shallow settings, or, in places, by relatively small bowl-shaped basins. The latter may have been strongly affected by the pre-existing topography and tectonics, as they developed at or near the leading edges of pre-Neogene substrate thrusts. These early deposits represent sedimentation during a transitional period from the end of compressional tectonics to the start of an extensional phase and represent a pre-narrow rift stage of evolution of the region. The subsequent stage of tectonic evolution (late Tortonian to early Messinian), where preserved, is recorded by fault-bounded triangular-shaped basins interpreted as half-grabens. This is one of the periods of major development of narrow rifts in the area. The following stage (late Messinian to Early Pliocene) is marked by variable types of basins, showing wide and deep bowl-shaped geometries persistent in the offshore, whereas inshore (Volterra Basin) they alternate with half-graben, synrift deposits. This period thus represents a transitional stage where part of the system is still affected by synrift sedimentation and part is developing into incipient post-rift conditions. This stage was followed in early to middle Pliocene times by wide bowl-shaped to blanket-type deposits both in offshore and in inshore areas, indicating regional post-rifting conditions. The pre-, syn- and post-rift stages have followed each other through time and space, starting first in the westernmost offshore area and shifting later toward the east, inshore.  相似文献   

New coring study in Augusta Bay expands understanding of offshore tsunami deposits (Eastern Sicily,Italy)     

Alessandra Smedile  Flavia Molisso  Catherine Chagué  Marina Iorio  Paolo Marco De Martini  Stefania Pinzi  Philip E. F. Collins  Leonardo Sagnotti  Daniela Pantosti 《Sedimentology》2020,67(3):1553-1576

Tsunami deposits present an important archive for understanding tsunami histories and dynamics. Most research in this field has focused on onshore preserved remains, while the offshore deposits have received less attention. In 2009, during a coring campaign with the Italian Navy Magnaghi, four 1 m long gravity cores (MG cores) were sampled from the northern part of Augusta Bay, along a transect in 60 to 110 m water depth. These cores were taken in the same area where a core (MS06) was collected in 2007 about 2·3 km offshore Augusta at a water depth of 72 m below sea level. Core MS06 consisted of a 6·7 m long sequence that included 12 anomalous intervals interpreted as the primary effect of tsunami backwash waves in the last 4500 years. In this study, tsunami deposits were identified, based on sedimentology and displaced benthic foraminifera (as for core MS06) reinforced by X-ray fluorescence data. Two erosional surfaces (L1 and L2) were recognized coupled with grain-size increase, abundant Posidonia oceanica seagrass remains and a significant amount of Nubecularia lucifuga, an epiphytic sessile benthic foraminifera considered to be transported from the inner shelf. The occurrence of Ti/Ca and Ti/Sr increments, coinciding with peaks in organic matter (Mo incoherent/coherent) suggests terrestrial run-off coupled with an input of organic matter. The L1 and L2 horizons were attributed to two distinct historical tsunamis (ad 1542 and ad 1693) by indirect age-estimation methods using ²¹⁰Pb profiles and the comparison of Volume Magnetic Susceptibility data between MG cores and MS06 cores. One most recent bioturbated horizon (Bh), despite not matching the above listed interpretative features, recorded an important palaeoenvironmental change that may correspond to the ad 1908 tsunami. These findings reinforce the value of offshore sediment records as an underutilized resource for the identification of past tsunamis.  相似文献