71 research outputs found
A generalized zero-lag cross-correlation approach for Rapid Earthquake Localization (REL): the example of the Istanbul Megacity Rapid Response System
No full text
Tsunami modeling of a submarine landslide in the Fram Strait
No full textThe present geological setting west of Svalbard closely parallels the situation off mid-Norway after the last glaciation, when crustal unloading by melting of ice induced very large earthquakes. Today, on the modern Svalbard margin, increasing bottom water temperatures are destabilizing marine gas hydrates, which are held in continental margin sediments consisting of interlayered contourite deposits and glacigenic debris flows. Both unloading earthquakes and hydrate failure have been identified as key factors causing several megalandslides off Norway during early Holocene deglaciation. The most prominent event was the Storegga Slide 8200 years B.P. which caused a tsunami up to 23 m high on the Faroe and Shetland islands. Here we show by numerical tsunami modeling that a smaller submarine landslide west of Svalbard, 100 m high and 130 km wide, would cause a tsunami capable of reaching northwest Europe and threatening coastal areas. A tsunami warning system based on tiltmeters would give a warning time of 1–4 h
Evaluation of proxies for seismic site conditions in large urban areas: The example of Santiago de Chile.
No full textCharacterizing the local site response in large cities is an important step towards seismic hazard assessment. To this regard, single station seismic noise measurements were carried out at 146 sites in the northern part of Santiago de Chile. This extensive survey allowed the fundamental resonance frequency of the sedimentary cover, derived from horizontal-to-vertical (H/V) spectral ratios, to be mapped. By inverting the spectral ratios under the constraint of the thickness of the sedimentary cover, known from previous gravimetric measurements, local S-wave velocity profiles have been retrieved. After interpolation between the individual profiles, the resulting high resolution 3D S-wave velocity model allows the entire area, as well as deeper parts of the basin, to be represented in great detail. Since one lithology shows a great scatter in the velocity values only a very general correlation between S-wave velocity in the uppermost 30 m (View the MathML source
) and local geology is found. Local S-wave velocity profiles can serve as a key factor in seismic hazard assessment, since they allow an estimate of the amplification potential of the sedimentary cover. Mapping the intensity distribution of the 27 February 2010 Maule, Chile, event (Mw = 8.8) the results indicate that local amplification of the ground motion might partially explain the damage distribution and encourage the use of the low cost seismic noise techniques for the study of seismic site effects
Spatio-temporal variability of seismic noise above a geothermal reservoir
No full textWe report on the application of seismic noise investigations, including H/V (horizontal to vertical) spectral ratio and array techniques, to a shallow gas-rich geothermal reservoir in Heybeli, southwestern Turkey. Fundamental resonant frequencies were determined to estimate the sediment thickness. Using small-scale seismic arrays, phase velocity dispersion curves were derived by correlating noise recordings according to the extended spatial autocorrelation method. Improved shear wave velocity profiles were estimated by combining Rayleigh wave dis- persion curves and horizontal to vertical spectral ratios in a joint inversion. We found that the velocities obtained for the reservoir site are higher than those for a location outside the reservoir. In addition to the fundamental res- onant peaks in the spectra, a clear 6-Hz-signal could be identified originating from the center of the geothermal field, repeatedly observed in 2010 and 2011. It had been claimed that low frequency (1–10 Hz) seismic signal anomalies were correlated with the occurrence of hydrocarbons. One of the physical mechanisms under consid- eration to explain these tremor-like signals above such reservoirs is resonant amplification due to the oscillation of bubbles. Based on the signal similarity with volcanic tremors, it is not a priori given that the liquid phase must be oil for resonance effects to occur. We therefore applied array techniques to identify potential noise originating from the Heybeli reservoir. In fact, the frequency–wavenumber (f–k) method clearly indicated a noise source coming from the main production well of the reservoir. In 2011, as part of our assessment, the operators of the spa facility stopped the extraction of thermal water for 2 h: the 6-Hz-signal disappeared after the pump had been stopped and reappeared after the pump began operating again. Thus, the 6-Hz-signal is likely of artificial origin. In addition, no natural noise source inside the reservoir could be identified
De. Condictione L. Si quis Conductionis. 25. C. de locato conducto. Sub Praesidio Dn. Andreae Mylii ... Publice disputabit. Author. Johann Gottfried Schönfeld/ Zitt. Lus. die 11. Iunii. M.DC.XCVI.
No full textDE. CONDICTIONE L. SI QUIS CONDUCTIONIS. 25. C. DE LOCATO CONDUCTO. SUB PRAESIDIO DN. ANDREAE MYLII ... PUBLICE DISPUTABIT. AUTHOR. JOHANN GOTTFRIED SCHÖNFELD/ ZITT. LUS. DIE 11. IUNII. M.DC.XCVI.
De. Condictione L. Si quis Conductionis. 25. C. de locato conducto. Sub Praesidio Dn. Andreae Mylii ... Publice disputabit. Author. Johann Gottfried Schönfeld/ Zitt. Lus. die 11. Iunii. M.DC.XCVI. (1)
Titelblatt (1)
Cap. I. - IV. (3)
Cap. V. - IIX. (13
New Multi-Hazard and Multi-Risk Assessment Methods for Europe. Risk governance and the communication process from science to policy: Evaluating perceptions of stakeholders from practice in multi-hazard and multi-risk decision support models: MATRIX results II and Reference Report
No full textModelling basin effects on earthquake ground motion in the Santiago de Chile basin by a spectral element code
No full textSimulations of strong ground motion within the Santiago de Chile Metropolitan area were
carried out by means of 3-D deterministic wave propagation tool based on the spectral element
method. The simulated events take into account the pronounced interface between the lowvelocity
sedimentary basin and the bedrock as well as topography of the area. To verify
our model we simulated a regional earthquake recorded by a dense network installed in the
city of Santiago for recording aftershock activity after the 2010 February 27 Maule main shock. The results proof the alluvial basin amplification effects and show a strong dependence
of spectral amplification in the basin on the local site conditions. Moreover, we studied the seismic response due to a hypothetical Mw = 6.0 event occurring along the active San Ram ́on Fault, which is crossing the eastern edge of the city. The scenario earthquakes exhibit that an unfavourable interaction between fault rupture, radiation mechanism and complex geological and topographic conditions in the near-field region may give rise to large values of peak ground velocity in the basin. Finally, 3-D numerical predictions of ground motion are compared with the one computed according to ground motion prediction equations selected among the next generation attenuation relationships, in terms of ground motion peak values and spectral acceleration. The comparison underlines that the 3-D scenario simulations predict a significantly higher level of ground motion in the Santiago basin, especially over deep alluvial deposits. Moreover, also the location of the rupture nucleation largely influences the observed
shaking pattern
Satellite-based forest fire detection and automatic alert system:Pilot Experiment
No full textA fully automatic system has been developed to detect forest fires using data from the meteorological NOAA satellites. The system has been tested in four pilot experiments in 1994–1998 in Finland and its neighbouring countries Estonia, Latvia, Russian Carelia, Sweden and Norway. For each detected fire, a telefax including data on the location of the fire, the observation time and a map showing the location, is sent directly to the local fire authorities. The area of the smallest forest fires detected was 0.1 ha. The time delay between receiving the NOAA scene and the sending of the fire alert was 31 min in average. Nearly all detected fires were forest fires or prescribed burnings. In the pilot experiment of the summer 1997 363 fires were observed and alerted. The verification showed that 83% of the given alerts concerned real fires. According to the authorities, none of the real significant forest fires in Finland remained undetected. The good verification results show that satellite-based detection system of forest fires is reliable, fast and cost effective, and it has potential in sparsely populated areas if continuous supply of middle-infrared satellite data can be guaranteed in the future. Because of the ecological and human necessity, fire monitoring and alert system on a global scale should be established urgently. For this purpose dedicated fire detection instruments and satellites should be developed
- …
