Is the seismic moment–frequency relation universal?     

C. Godano  & F. Pingue 《Geophysical Journal International》2000,142(1):193-198

We evaluate the seismic moment–frequency relation for the Harvard catalogue in the period 1977–1994. This catalogue is composed of about 12 000 earthquakes. After selection of events in terms of depth and energy, we retain about 8000 data points. We estimate two parameters of the seismic moment distribution: the power exponent β and the cut-off value M _m . The method used is a least-squares linear fit on a log–log scale performed over a range selected on the basis of the standard deviation from the histogram. The analysis is carried out for different subdivisions of the Earth in square grids of different sizes. Neither parameter exhibits a dependence on cell size, suggesting the universality of their values and the interpretation of the existence of a cut-off as a finite size effect linked to a finite catalogue length. The variations of the parameters are investigated as a function of time (duration of the catalogue) and versus the number of events used for building up the distribution. Again, β and M _m do not depend on time, but M _m depends on the number of events, reaching a stable value for N ≈ 1000. The only significant change in the parameters is observed for different values of M _0upper in the catalogue, revealing the existence of universality classes.  相似文献   

Fission track age of Transantarctic Mountain microtektites     

L. Folco  G. Bigazzi  M.L. Balestrieri 《Geochimica et cosmochimica acta》2011,75(9):2356-6210

We determined the fission track age of Transantarctic Mountain microtektites. The plateau method yielded a formation age of 0.85 ± 0.17 Ma. This age overlaps within error with that of the catastrophic impact that produced the Australasian tektite-microtektite strewn field ca. 0.8 Ma ago. This provides further evidence that Transantarctic Mountain microtektites belong to the Australasian tektite-microtektite strewn field, as previously suggested on the basis of geochemical evidence, Sr-Nd isotope systematics and poorly resolved radiometric data.  相似文献   

Major, trace element and oxygen isotope study of glass cosmic spherules of chondritic composition: The record of their source material and atmospheric entry heating     

Carole Cordier  Luigi Folco  Corinne Sonzogni 《Geochimica et cosmochimica acta》2011,75(18):5203-6210

New geochemical data on cosmic spherules (187 major element, 76 trace element, and 10 oxygen isotope compositions) and 273 analyses from the literature were used to assess the chemical diversity observed among glass cosmic spherules with chondritic composition. Three chemical groups of glass spherules are identified: normal chondritic spherules, CAT-like spherules (where CAT refers to Ca-Al-Ti-rich spherules), and high Ca-Al spherules. The transition from normal to high Ca-Al spherules occurs through a progressive enrichment in refractory major elements (on average from 2.3 wt.% to 7.0 wt.% for CaO, 2.8 wt.% to 7.2 wt.% for Al₂O₃, and 0.14 wt.% to 0.31 wt.% for TiO₂) and refractory trace elements (from 6.2 μg/g to 19.3 μg/g for Zr and 1.6CI-4.3CI for Rare Earth Elements-REEs) relative to moderately refractory elements (Mg, Si) and volatile elements (Rb, Na, Zn, Pb). Based on a comparison with experimental works from the literature, these chemical groups are thought to record progressive heating and evaporation during atmospheric entry. The evaporative mass losses evaluated for the high Ca-Al group (80-90%) supersede those of the CAT spherules which up to now have been considered as the most heated class of stony cosmic spherules. However, glass cosmic spherules still retain isotopic and elemental evidence of their source and precursor mineralogy. Four out of the 10 normal and high Ca-Al spherules analysed for oxygen isotopes are related to ordinary chondrites (δ¹⁸O = 13.2-17.3‰ and δ¹⁷O = 7.6-9.2‰). They are systematically enriched in Ni and Co (Ni = 24-500 μg/g) with respect to spherules related to carbonaceous chondrites (Ni < 1.2 μg/g, δ¹⁸O = 13.1-28.0‰ and δ¹⁷O = 5.1-14.0‰). REE abundances in cosmic spherules, which are not fractionated according to parent body or atmospheric entry heating, can then be used to unravel the precursor mineralogy. Spherules with flat REE pattern close to unity when normalized to CI are the most abundant in our dataset (54%) and likely derive from homogeneous, fine-grained chondritic precursors. Other REE patterns fall into no more than five categories, a surprising reproducibility in view of the mineralogical heterogeneity of chondritic lithologies at the micrometeorite scale.  相似文献   

The VLTI – A Status Report     

A. Glindemann  J. Algomedo  R. Amestica  P. Ballester  B. Bauvir  E. Bugueño  S. Correia  F. Delgado  F. Delplancke  F. Derie  Ph. Duhoux  E. di Folco  A. Gennai  B. Gilli  P. Giordano  Ph. Gitton  S. Guisard  N. Housen  A. Huxley  P. Kervella  M. Kiekebusch  B. Koehler  S. Lévêque  A. Longinotti  S. Ménardi  S. Morel  F. Paresce  T. Phan Duc  A. Richichi  M. Schöller  M. Tarenghi  A. Wallander  M. Wittkowski  R. Wilhelm 《Astrophysics and Space Science》2003,286(1-2):35-44

The Very Large Telescope (VLT) Observatory on Cerro Paranal (2635 m) in Northern Chile is approaching completion. After the four 8-m Unit Telescopes (UT) individually saw first light in the last years, two of them were combined for the first time on October 30, 2001 to form a stellar interferometer, the VLT Interferometer. The combination in pairs of all four UTs was completed in September 2002. In this article, we will describe the subsystems of the VLTI and the planning for the following years. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Chondrule thermal history from unequilibrated H chondrites: A transmission and analytical electron microscopy study     

C. Ferraris  L. Folco  M. Mellini 《Meteoritics & planetary science》2002,37(10):1299-1321

Abstract— Sixteen texturally different (porphyritic, barred, radial, cryptocrystalline) FeO‐rich chondrules from the unequilibrated ordinary chondrites Brownfield, Frontier Mountain (FRO) 90003 and FRO 90032 were characterized by optical and scanning electron microscopy and then thoroughly studied by transmission and analytical electron microscopy. Nanotextural and nanochemical data indicate similar thermal evolution for chondrules of the same textural groups; minor, yet meaningful differences occur among the different groups. Olivine is the earliest phase formed and crystallizes between 1500 and 1400 °C. Protoenstatite crystallizes at temperatures higher than 1350–1200 °C; it later inverts to clinoenstatite in the 1250–1200 °C range. Enstatite is surrounded by pigeonitic or (less frequently) augitic rims; the minimal crystallization temperature for the rims is 1000 °C; high pigeonite later inverts to low pigeonite, between 935 and 845 °C. The outer pigeonitic or augitic rims are constantly exsolved, producing sigmoidal augite or enstatite precipitates; sigmoidal precipitates record exsolution temperatures between 1000 and 640 °C. Cooling rate (determined using the speedometer based upon ortho‐clinoenstatite intergrowth) was in the order of 50–3000 °C/h at the clinoenstatite‐orthoenstatite transition temperature (close to 1250–1200 °C), but decreased to 5–10 °C/h or slower at the exsolution temperature (between 1000 and 650 °C), thus revealing nonlinear cooling paths. Nanoscale observations indicate that the individual chondrules formed and cooled separately from 1500 °C down to at least 650 °C. Accretion into chondritic parent body occurred at temperatures lower than 650 °C.  相似文献   

Meteoritic and bedrock constraints on the glacial history of Frontier Mountain in northern Victoria Land, Antarctica   总被引：2，自引：0，他引：2  

K.C. Welten  L. Folco  K. Nishiizumi  M.W. Caffee  A. Grimberg  M.M.M. Meier  F. Kober 《Earth and Planetary Science Letters》2008,270(3-4):308-315

In 2001, a small H4 chondrite, Frontier Mountain (FRO) 01149, was found on a glacially eroded surface near the top of Frontier Mountain, Antarctica, about 600 m above the present ice level. The metal and sulphides are almost completely oxidized due to terrestrial weathering. We used a chemical leaching procedure to remove weathering products, which contained atmospheric ¹⁰Be and ³⁶Cl in a ratio similar to that found in Antarctic ice. The FRO 01149 meteorite has a terrestrial age of 3.0 ± 0.3 Myr based on the concentrations of the cosmogenic radionuclides ¹⁰Be, ²⁶Al and ³⁶Cl. This age implies that FRO 01149 is the oldest stony meteorite (fossil meteorites excluded) discovered on Earth. The noble gas cosmic ray exposure age of FRO 01149 is ~ 30 Myr. The meteorite thus belongs to the 33 Myr exposure age peak of H-chondrites.The bedrock surface on which FRO 01149 was found has wet-based glacial erosional features recording a former high-stand of the East Antarctic ice sheet. This ice sheet evidently overrode the highest peaks (> 2800 m a.s.l.) of the inland sector of the Transantarctic Mountains in northern Victoria Land. We argue that FRO 01149 was a local fall and that its survival on a glacially eroded bedrock surface constrains the age of the last overriding event to be older than ~ 3 Myr. The concentrations of in-situ produced cosmogenic ¹⁰Be, ²⁶Al and ²¹Ne in a glacially eroded bedrock sample taken from near the summit of Frontier Mountain yield a surface exposure age of 4.4 Myr and indicate that the bedrock was covered by several meters of snow. The exposure age is also consistent with bedrock exposure ages of other summit plateaus in northern Victoria Land.  相似文献   

Structure and dynamics of the Somma-Vesuvius volcanic complex     

G. De Natale  C. Troise  F. Pingue  P. De Gori  C. Chiarabba 《Mineralogy and Petrology》2001,73(1-3):5-22

Summary We review recently obtained results about the velocity structure of the Somma-Vesuvius (Southern Italy) volcanic complex and present an interpretation of structural features, both at local and regional scale, and of the local seismicity. The local structure of Somma-Vesuvius is reviewed, referring to three depth ranges; i.e. shallow (0–5 km), intermediate (5–15 km) and deep (from 15 km to the upper mantle). The shallow velocity structure is inferred by the joint inversion of shot and local earthquake arrival time data. The main feature pointed out by this inversion is a high-velocity anomaly at the crater axis extending down to a depth of about 5 km. This anomaly can be explained with the presence of residual magma crystallised in the shallow conduits, which accumulated during the last eruptive cycles. The local seismicity is strongly clustered around this anomaly, due to the focusing effect of the rigidity contrast. The space-time seismicity pattern at Somma-Vesuvius is the result of the superposition of background seismicity, mainly due to gravitational instability of the volcanic edifice and to small external stress perturbations, with intense episodic earthquake swarms possibly due to magmatic or hydrothermal activity into the shallow system. The velocity structure in the 10–15 km depth range is characterized by the presence of a low-velocity layer, which has been independently confirmed by multi-channel seismic reflection data and P-Sv conversions from teleseismic waveforms. The study of the deep structure was performed by regional tomography with teleseisms; it confirmed the presence of a low-velocity anomaly underneath the volcano, which appears to have roots at greater depths. The regional structure between the Thyrrenian and the Adriatic sea has been inferred by tomographic inversion of teleseismic arrival times. The main result from this study which is very important for geodynamic interpretations is the first evidence for a continuous subducting slab under the Apennines, in an area where previous models hypothesized a slab window. Received March 3, 2000 revised version accepted July 4, 2001  相似文献   

Recent terrestrial and satellite observations to model deformations at Colli Albani volcano (central Italy)     

F. Riguzzi  S. Atzori  F. Obrizzo  G. Pietrantonio  F. Pingue 《International Journal of Earth Sciences》2012,101(6):1661-1671

The Colli Albani volcanic complex (Rome, Italy) has been dominated by episodic eruptions commencing around 561?ka and ending with the most recent activity of the Albano maar phase (<70?ka). Earthquakes of moderate intensity, gas emissions and significant ground deformations are the recent evidences of a residual activity. Former geodetic data from leveling surveys, GPS stations and InSAR observations tracked ongoing significant uplift of the order of few mm/year near the Colli Albani western flank. Different uplift rates were detected by each technique in different time spans, suggesting also the possibility of sporadic recharge of the hydrothermal system. The renewed high precision leveling data from IGMI survey carried out in 1997/1999 and the last leveling survey carried out in 2006 show that the uplift along the route is currently significant at an average rate of ~3?mm/year. Radar interferograms from ALOS satellite show uplift rate of ~6?mm/year, southwest of the central sector of the leveling route. We have undertaken a joint inversion of the various geodetic data (vertical rates from leveling surveys, GPS site velocities and InSAR observations acquired by ALOS satellite) using a nonlinear inversion technique to estimate the parameters of a point-pressure source, possibly capable of explaining the ongoing deformation at Colli Albani volcano.  相似文献   

Shock metamorphism and impact melting in small impact craters on Earth: Evidence from Kamil crater,Egypt     

Agnese Fazio  Luigi Folco  Massimo D'Orazio  Maria Luce Frezzotti  Carole Cordier 《Meteoritics & planetary science》2014,49(12):2175-2200

Kamil is a 45 m diameter impact crater identified in 2008 in southern Egypt. It was generated by the hypervelocity impact of the Gebel Kamil iron meteorite on a sedimentary target, namely layered sandstones with subhorizontal bedding. We have carried out a petrographic study of samples from the crater wall and ejecta deposits collected during our first geophysical campaign (February 2010) in order to investigate shock effects recorded in these rocks. Ejecta samples reveal a wide range of shock features common in quartz‐rich target rocks. They have been divided into two categories, as a function of their abundance at thin section scale: (1) pervasive shock features (the most abundant), including fracturing, planar deformation features, and impact melt lapilli and bombs, and (2) localized shock features (the least abundant) including high‐pressure phases and localized impact melting in the form of intergranular melt, melt veins, and melt films in shatter cones. In particular, Kamil crater is the smallest impact crater where shatter cones, coesite, stishovite, diamond, and melt veins have been reported. Based on experimental calibrations reported in the literature, pervasive shock features suggest that the maximum shock pressure was between 30 and 60 GPa. Using the planar impact approximation, we calculate a vertical component of the impact velocity of at least 3.5 km s^?1. The wide range of shock features and their freshness make Kamil a natural laboratory for studying impact cratering and shock deformation processes in small impact structures.  相似文献   

A field trial to test the efficiency of induced partial saturation and horizontal drains to mitigate the susceptibility of soils to liquefaction     

Flora  A.  Bilotta  E.  Chiaradonna  A.  Lirer  S.  Mele  L.  Pingue  L. 《Bulletin of Earthquake Engineering》2021,19(10):3835-3864

Within the European project LIQUEFACT some activities have been devoted to the experimental verification of the effectiveness of two techniques in the mitigation of soil liquefaction susceptibility: induced partial saturation (IPS) and horizontal drains. After a preliminary check of their efficiency via centrifuge tests, the two techniques have been studied by means of some large scale shaking tests carried out in a field trial located in the Emilia-Romagna Region (Italy). A preliminary extensive in situ and laboratory investigation was necessary to identify the shallow liquefiable soil layer in which the mitigation techniques and the monitoring instrumentations (pore pressure transducers and geophones) had to be installed. Both techniques required the installation of horizontal well screens via a directional controlled drilling technique: the pipes were used as drainage systems (linear HDL and rhomboidal configurations HDR) or for the air injection in the area treated with IPS technique. The in situ experimental evidences showed that both techniques are able to avoid liquefaction triggering, that on the contrary was attained during the tests in the untreated testing area. The processing of in situ data highlighted that the efficiency of the two techniques is strictly related to chosen arrangement of the horizontal drains and the induced degree of saturation.

  相似文献