Antonella Amoruso

Inversion of source parameters from near‐ and far‐field observations: An application to the 1915 Fucino earthquake, central Apennines, Italy

We use a nonlinear inversion approach for determining source parameters of the Fucino Ms=6.9 earthquake that occurred along central Apennines, Italy, in 1915, taking into account both near-field surface deformations and far-field first-motion polarities. This event was one of the most destructive in Italy this century, causing over 30,000 casualties. Altitude and leveling measurements were performed before (1862) and after (1917) the event, along a circular route consisting of 18 benchmarks. Polarities of first arrivals do not constrain a unique fault-plane solution, while the one obtained by inverting geodetic data, with relevant constraints provided by neotectonic data, disagrees with P wave polarities. Our joint inversion, based on a robust fitting technique, has resulted in only one well-defined solution, satisfying geophysical data as well as surface-faulting distribution and paleoseismological information.

Installation of a high-sensitivity laser strainmeter in a tunnel in central Italy

A new laser interferometer for geophysical purposes is being operated in an underground laboratory in central Italy. A simple electro-optical technique has been used to limit the costs. The main characteristics of this instrument are: high sensitivity (Δl/l≈10−12), fast sampling rate (up to 6 kHz), large dynamic range (unbounded in principle), the capability of following strain rates as high as 7×10−5 s−1, and good reliability (two failures in nearly two years).

Oxygen absorption cross-section in the Herzberg continuum

Abstract A new set of measurements of the absorption cross-section of oxygen in the wavelength range 208–240 nm is reported. These new data, obtained using a 90 m long cell, are about 15% lower than the most recently published.

New measurements of the NO2 absorption cross section in the 440‐ to 460‐nm region and estimates of the NO2‐N2O4 equilibrium constant

Absolute determinations of the NO2 absorption cross section in the 440- to 460-nm region at different temperatures are reported. This region is of special interest for remote sensing applications. The interpretation of the results is rendered complex by the coexistence of NO2 and its dimer. In the experiment both NO2 and N2O4 absorption features are observed. Different approaches are utilized to obtain the partial pressure of NO2; a new estimate of the NO2-N2O4 equilibrium constant from spectroscopic measurements is also obtained. Within experimental errors the overall shape of the spectrum does not show a dependence on temperature, but some features are affected; in particular, a slight increase of a few maxima and a decrease of the other maxima and of the minima when the temperature is lowered have been observed.

New borehole strain system detects uplift at Campi Flegrei

Campi Flegrei and Mount Vesuvius are active Italian volcanoes though presently in aquiescent stage. The last eruption of Mount Vesuvius occurred during the spring of 1944. Campi Flegrei last erupted in 1538 but experienced a subsidence trend from the early 1900s to 1970, which was followed by episodes of ground uplift accompanied by seismic swarms [see, e.g., Aster et al., 1992]. Over the past 37 years at Campi Flegrei, about 4 meters of maximum ground uplift has occurred followed by about 1 meter of subsidence, as measured near the center of the caldera in two episodes during 1970–1972 and 1982–1984. This deformation has occurred close to the harbor of the town of Pozzuoli, putting about 400,000 people at heightened risk. From 1985 to 2004, Campi Flegreis caldera showed gradual subsidencethat was interrupted by five mini-uplift episodesin 1976, 1989, 1995, 2000, and, most recently, 2004–2006, each amounting to a few centimeters of uplift [Pingue et al., 2006]. The caldera is generally aseismic during gradual subsidence, but small swarms of microearthquakes are produced during periods of elevated strain rates associated with the mini-uplift episodes [Saccorotti et al., 2001 ].

Nonlinear and minor ocean tides in the Bay of Biscay from the strain tides observed by two geodetic laser strainmeters at Canfranc (Spain)

This work presents and discusses the tidal analysis of about 2.5 years of strain data recorded by two 70 m-long high-resolution laser strainmeters, which are operating in the Canfranc underground laboratory (Central Pyrenees, Spain). Spectra show clear tidal peaks whose frequencies range from the diurnal band to at least 8 cycles per day; strain amplitudes (relative change in length for each strainmeter) range from few 10−12 to 10−8. The reliability of observations and corrections for local distortions are testified by the excellent agreement between measurements and computations for all the diurnal and semidiurnal tides included in the TPXO8 and FES2012 tidal atlases, with the exception of L2. Observed higher-frequency strain tides are mostly attributed to loading by nonlinear shallow-water constituents in the Bay of Biscay, more than 120 km from the measurement site. The signals are quantitatively compared with computations using TPXO8 (MN4, M4, and MS4) and FES2012 (M3, N4, MN4, M4, MS4, and M6). Computations fully agree with M4 observations for one strainmeter, overestimate M4 by about 30% for the other strainmeter and M6 by about a factor of two, and underestimate the other tides. This work shows that data from high-sensitivity strainmeters installed in high-quality sites may provide valuable additional information for studying the nonlinear tidal dynamics and energetics of coastal waters and minor ocean tides, at spatial resolutions of tens to thousands square kilometers, depending on the strainmeter location with respect to the coastline.

Improving the SOPRA DMDP2000 spectrometer by a Michelson interferometer

A new class of multiple dispersion grating spectrometer was commercialized a few years ago (SOPRA DMDP2000). In practice, mechanical tolerances do not let it operate at its very best characteristics. The instrument can be considerably improved by using a simple Michelson interferometer.

Oxygen dimerization and pressure dependence of the absorption cross-section in the Herzberg continuum

Abstract Using experimental data available on the dependence of the absorption cross-section of O2 on pressure in the Herzberg continuum, the equilibrium constant of oxygen dimerization has been estimated. The results show that the formation of the oxygen dimer, if it occurs according to the equilibrium constant calculated from the second virial coefficient, cannot account for the pressure dependence of the absorption cross-section of oxygen.

Oceanic Loading and Local Distortions at the Baksan, Russia, and Gran Sasso, Italy, Strain Stations

Reliable use of strain data in geophysical studies requires their preliminary correction for ocean loading and various local distortions. These effects, in turn, can be estimated from the tidal records which are contributed by solid and oceanic loading. In this work, we estimate the oceanic tidal loading at two European strain stations (Baksan, Russia, and Gran Sasso, Italy) by analyzing the results obtained with the different Earth and ocean models. The influence of local distortions on the strain measurements at the two stations is estimated.