Stacked analysis of earthquake sequences: statistical space-time definition of clustering and Omori law behavior

The definition of the aftershocks sequence is still a debated topic. We here propose a study of the spatial and temporal variation of the earthquakes clustering and rate decay. We used five different seismic catalogues, characterized by specific spatial and magnitude ranges. They are respectively: world one, for a global analysis, Greek, Japanese, Californian and Italian regional catalogues in order to investigate different seismo-tectonic settings. A stacking procedure has been applied to characterize a typical sequence behavior and allowing the evaluation of changes over time intervals

Earthquake sound perception

Sound is an effect produced by almost all earthquakes. Using a web-based questionnaire on earthquake effects that included questions relating to seismic sound, we collected 77,000 responses for recent shallow Italian earthquakes. An analysis of audibility attenuation indicated that the decrease of the percentage of respondents hearing the sound was proportional to the logarithm of the epicentral distance and linearly dependent on earthquake magnitude, in accordance with the behavior of ground displacement. Even if this result was based on Italian data, qualitative agreement with the results of theoretical displacement, and of a similar study based on French seismicity suggests wider validity. We also found that, given earthquake magnitude, audibility increased together with the observed macroseismic intensity, leading to the possibility of accounting for sound audibility in intensity assessment. Magnitude influenced this behavior, making small events easier to recognize, as suggested by their frequency content

How Observer Conditions Impact Earthquake Perception

Intensity scales define the criteria used to determine different levels of shaking in relation to environmental effects. Objective evaluations of low intensity degrees based on transient effects may be difficult. In particular, estimations for the number of people feeling an earthquake are critical, and are qualitatively described by words such as “few”, “many”, and “most” for determining various intensity levels. In general, such qualitative amounts are converted into specific percentages for each macroseismic scale. Additionally, estimations of macroseismic intensity are influenced by variables that are mentioned in macroseismic scale degree descriptions. For example, the Mercalli-Cancani-Sieberg (MCS; Sieberg, 1930) and the Modified Mercalli Intensity (MMI) scales (Wood and Neumann, 1931) describe the intensity II as “Felt only by a few people, extremely susceptible, in perfectly quiet situations, almost always on the upper floors of buildings”. Another example is the European Macroseismic Scale (EMS) (Grunthal, 1998) that describes the intensity V as “felt indoors by most, outdoors by few. Many sleeping people awake”. In this work, we focus on two variables referred to as people’s physical “situation” (what were you doing?), here categorized as “sleeping”, “at rest”, or “in motion”; and the observer’s “location”, here categorized as “higher floors”, “lower floors”, and “outdoors”. Both variables have a partial influence on intensity assessments because they condition vibration perception. However, it is important to study, using an experimental method, the weights of these variables in the quantification of felt effects. Musson (2005a) also recognized the influence of such conditions on the number of people feeling an earthquake, stating that the proportion of people in different conditions “are generally difficult to quantify in any case”. Today, we have a large amount of data available through the macroseismic web site “haisentitoilterremoto” associated with specific observer conditions. Using this data, a study of these effects is possible. For this analysis, we placed attention on transitory effects that, in the past, could not be easily studied due to the intrinsic difficulty in collecting this type of data. The aim of this work was to specifically analyze and quantify how the observer’s “situation” and “location” influence earthquake perception suggesting a new scale description that can be easily used for low intensity estimation

Web-based macroseismic survey in Italy: method validation and results

A new method of macroseismic surveys, based on voluntary collaboration through the Internet, has been running at the Istituto Nazionale di Geofisica e Vulcanologia (INGV) since July 2007. The macroseismic questionnaire is addressed to a single non-specialist; reported effects are statistically analysed to extrapolate a probabilistic estimate of Mercalli Cancani Sieberg and European Macroseismic Scale intensities for that observer. Maps of macroseismic intensity are displayed online in almost real time and are continuously updated when new data are made available. For densely inhabited zones, we have received reports of felt effects for even very small events (M=2). Six earthquakes are presented here, showing the ability of the method to give fast and interesting results. The effects reported in questionnaires coming from three towns are carefully analysed and assigned intensities are compared with those derived from traditional macroseismic surveys, showing the reliability of our web-based method

Influence of observation floor and building height on macroseismic intensity

The perception of an earthquake depends on whether the observer is located on a lower or upper floor within a building. Macroseismic scales propose only a qualitative description of the varying effects felt that are dependent on the floor the observer is on. To quantify these effects, in this study, we analyze 45,000 macroseismic questionnaires collected in Italy reporting on transitory effects. The questionnaires pertain to buildings no more than 10 stories high and are derived from municipalities experiencing a Mercalli-Cancani-Sieberg (MCS) intensity less than or equal to VII with the majority being III and IV. We find that the intensity variation caused by the increased shaking on upper floors can be quantified. The upper floor intensity increases by 0.4 MCS compared with ground and underground levels. After correcting for an average floor-dependence factor, we find a further building height effect evident in short buildings that are probably exposed to less intense shaking. This effect displays a variation with the hypocentral distance reaching an MCS intensity of -0.3 at distances on the order of 200 km

The power-law behaviours of angular spectra of polarized Galactic synchrotron

We study the angular power spectra of polarized Galactic synchrotron in the range 10<l<800, at several frequencies between 0.4 and 2.7 GHz and at several Galactic latitudes up to near the North Galactic Pole. Electric- and magnetic-parity polarization spectra are found to have slopes around alpha _{E,B} = 1.4 - 1.5 in the Parkes and Effelsberg Galactic-Plane surveys, but strong local fluctuations of alpha_{E,B} are found at | b | ~ 10 degree from the 1.4 GHz Effelsberg survey. The C_{PIl} spectrum, which is insensitive to the polarization direction, is somewhat steeper, being alpha_{PI} = 1.6 - 1.8 for the same surveys. The low-resolution multifrequency survey of Brouw and Spoelstra (1976) shows some flattening of the spectra below 1 GHz, more intense for C_{E,Bl} than for C_{PIl}. In no case we find evidence for really steep spectra. The extrapolation to the cosmological window shows that at 90 GHz the detection of E-mode harmonics in the cosmic background radiation should not be disturbed by synchrotron, even around l~10 for a reionization optical depth tau _{ri}>~0.05.Comment: 20 pages, 9 figures, accepted to New Astronom

How precisely will the total cross section be measured at the LHC?

It is very likely that hadronic scattering will enter a new regime at the LHC, as the black-disk limit is reached. This will lead to a severe change in the t dependence of the real part and of the slope of the elastic scattering amplitude, and in turn this may bias the measurement of the total cross section. We examine this issue, and suggest new strategies to test the reliability of the total cross section measurements.Comment: 4 pages, 6 figure

The AMS-02 Time of Flight System. Final Design

The AMS-02 detector is a superconducting magnetic spectrometer that will operate on the International Space Station. The time of flight (TOF) system of AMS-02 is composed by four scintillator planes with 8, 8, 10, 8 counters each, read at both ends by a total of 144 phototubes. This paper describes the new design, the expected performances, and shows preliminary results of the ion beam test carried on at CERN on October 2002.Comment: 4 pages, 6 EPS figures. Proc. of the 28th ICRC (2003

Macroseismic effects highlight site response in Rome and its geological signature

A detailed analysis of the earthquake effects on the urban area of Rome has been conducted for the L’Aquila sequence, which occurred in April 2009, by using an on-line macroseismic questionnaire. Intensity residuals calculated using the mainshock and four aftershocks are analyzed in the light of a very accurate and original geological reconstruction of the subsoil of Rome based on a large amount of wells. The aim of this work is to highlight ground motion amplification areas and to find a correlation with the geological settings at a sub-regional scale, putting in evidence the extreme complexity of the phenomenon and the difficulty of making a simplified model. Correlations between amplification areas and both near-surface and deep geology were found. Moreover, the detailed scale of investigation has permitted us to find a correlation between seismic amplification in recent alluvial settings and subsiding zones, and between heard seismic sound and Tiber alluvial sediments

The BaR-SPOrt Experiment

BaR-SPOrt (Balloon-borne Radiometers for Sky Polarisation Observations) is an experiment to measure the linearly polarized emission of sky patches at 32 and 90 GHz with sub-degree angular resolution. It is equipped with high sensitivity correlation polarimeters for simultaneous detection of both the U and Q stokes parameters of the incident radiation. On-axis telescope is used to observe angular scales where the expected polarization of the Cosmic Microwave Background (CMBP) peaks. This project shares most of the know-how and sophisticated technology developed for the SPOrt experiment onboard the International Space Station. The payload is designed to flight onboard long duration stratospheric balloons both in the Northern and Southern hemispheres where low foreground emission sky patches are accessible. Due to the weakness of the expected CMBP signal (in the range of microK), much care has been spent to optimize the instrument design with respect to the systematics generation, observing time efficiency and long term stability. In this contribution we present the instrument design, and first tests on some components of the 32 GHz radiometer.Comment: 12 pages, 10 figures, Astronomical Telescopes and Instrumentation (Polaimetry in Astronomy) Hawaii August 2002 SPIE Meetin