Results 1 - 10 of 1411
Results 1 - 10 of 1411. Search took: 0.032 seconds
|Sort by: date | relevance|
[en] Due to a procedural error in construction of Figs. 8 and 9, listed minimum speeds to beat the tsunami wave in areas of Seaside seaward of Neawanna Creek are too high. The two figures should be replaced by the new figures below.
[en] Tidal triggering of earthquakes is hypothesized to provide quantitative information regarding the fault's stress state, poroelastic properties, and may be significant for our understanding of seismic hazard. To date, studies of regional or global earthquake catalogs have had only modest successes in identifying tidal triggering. We posit that the smallest events that may provide additional evidence of triggering go unidentified and thus we developed a technique to improve the identification of very small magnitude events. We identify events applying a method known as inter-station seismic coherence where we prioritize detection and discrimination over characterization. Here we show tidal triggering of earthquakes on the San Andreas Fault. We find the complex interaction of semi-diurnal and fortnightly tidal periods exposes both stress threshold and critical state behavior. Lastly, our findings reveal earthquake nucleation processes and pore pressure conditions – properties of faults that are difficult to measure, yet extremely important for characterizing earthquake physics and seismic hazards.
[en] Recent observations of internal waves and currents generated by tidal mixing inside the strait of Messina, with classical measurements made in 1922-1923 by Francesco Vercelli are compared. A peculiar front South of Capo Vaticano in southern Tyrrhenian Sea is described. Its relation with the turbolence due to the braking of internal nonlinear waves generated by the inside the Strait of Messina is discussed
[en] This correction stands to correct Figure 7c listing a low minimum slip of 12 m for Case 2 instead of the correct value of 8 m, as stated in the body of the text and depicted on the chart of cumulative slip. The corrected chart explanation and caption are shown below. This error did not affect any of the findings of the paper or the chart itself. This is a correction to the original article.
[en] The Valais is the most seismically active region of Switzerland. Strong damaging events occurred in 1755, 1855, and 1946. Based on historical documents, we discuss two known damaging events in the sixteenth century: the 1524 Ardon and the 1584 Aigle earthquakes. For the 1524, a document describes damage in Ardon, Plan-Conthey, and Savièse, and a stone tablet at the new bell tower of the Ardon church confirms the reconstruction of the bell tower after the earthquake. Additionally, a significant construction activity in the Upper Valais churches during the second quarter of the sixteenth century is discussed that however cannot be clearly related to this event. The assessed moment magnitude Mw of the 1524 event is 5.8, with an error of about 0.5 units corresponding to one standard deviation. The epicenter is at 46.27 N, 7.27 E with a high uncertainty of about 50 km corresponding to one standard deviation. The assessed moment magnitude Mw of the 1584 main shock is 5.9, with an error of about 0.25 units corresponding to one standard deviation. The epicenter is at 46.33 N and 6.97 E with an uncertainty of about 25 km corresponding to one standard deviation. Exceptional movements in the Lake Geneva wreaked havoc along the shore of the Rhone delta. The large dimension of the induced damage can be explained by an expanded subaquatic slide with resultant tsunami and seiche in Lake Geneva. The strongest of the aftershocks occurred on March 14 with magnitude 5.4 and triggered a destructive landslide covering the villages Corbeyrier and Yvorne, VD.
[en] The tsunami which occurred on December 28, 1908, in the Straits of Messina is examined. A wide set of data coming from a number of sources was collected and reviewed in order to get a picture as clear as possible of the generation and evolution of the event. The tsunami magnitude is estimated according to the Murty-Loomis scale, based upon the evaluation of the initial wave disturbance energy
[en] Simultaneous meteor radar wind observations were made at Budrio (Italy,45 deg N), Sheffield (U.K.,53 deg N) and Stornoway (U.K.,58 deg N) during the Energy Budget Campaign (EBC), November-December 1980, in the altitude region between 75 and 115 km. Wind results are presented in terms of prevailing components an oscillations of different time scales: tidal (8,12 and 24 h), gravity ((3/6)h) and planetary ((2/10) days) waves. The seasonal variation of the prevailing zonal components observed at the three stations in previous years shows the same maxima of Summer and Winter, as well as the equinactial minima exhibited by the CIRA 19972 model for 50 deg N. The data show marked tidal activity with the semi-diurnal tide which exceeds in amplitrude any other mode in the wind spectra. Tidal amplitudes recorded at Budrio appear more significantly lower than those recorded at Sheffield and Stornoway. Variations of the amplitude of maxima of the semi-diurnal oscillation relative to the Budrio and Sheffield data show time scales generally greater than 5 days throughout the recording period. The diurnal and terdiurnal tides represent a small part of the total wind energy in the meteor zone and exhibit phases which disagree strongly at the quoted stations. The scatter in the hourly data is representative of small-scale wind disturbances due to internal gravity waves: at Budrio, by using the MEM method for individual day's data (November 23-24, 28-29, 1980), gravity waves with vertical wave-lengths of (20/45) km, periods of 3.5, 4.5 and 6 h, and amplitudes of the order of 10 ms-1 have been observed. Long-period oscillations with periods in the (2/10) day time interval have been identified in the wind patterns at Budrio and Sheffield, but the presence of planetary waves of quasi-2-day period was less significant than during a previous Summer 1980 run carried out at the same stations
[en] Complete text of publication follows. In this work, we present the results from CHAMP and COSMIC satellite measurements of neutral density, temperature, ionospheric density and electromagnetic disturbances in atmosphere and ionosphere registered before and during few Earthquakes/Tsunami. Three Sumatra tsunamis, SUM1 (26 Dec 2004, 00:58:53 UT, Mw=9.1, 3.31N, 95.85E), SUM2 (28 Mar 2005, 16:09:36 UT, Mw=8.6, 2.074N, 97.013E) and SUM3 (12 Sep 2007, 11:10:26 UT, Mw=8.5, 4.52S, 101.37E). For SUM1 and SUM2, CHAMP measurements of electromagnetic and electron density disturbances in the ionosphere are analyzed. For SUM3, COSMIC measurements of atmospheric and ionospheric disturbances are also analyzed. In first step, disturbances registered during these events are examined. In particular, their timespatial scale and spectral distributions are studied. Knowing these aspects, similar features, though in much reduced magnitudes and possibly in much slower timescale, are searched in the satellite data prior to these events. In this way, we could find disturbances which may be possibly associated with pre-tsunami activities. We also present computational simulation of possible excitation of disturbances near Earth's surface and in the atmosphere/ionosphere caused by tiny rock deformation in the lithosphere prior to an earthquake/tsunami. In first step, the study pursue an excitation of acoustic wave in the lithosphere caused by rock deformation, its propagation in solid Earth up-to Earth's surface and deposition of momentum and energy at the Earth's surface. In second step, excitation of neutral waves such as acoustic gravity waves (AGWs) caused by deposition of momentum/energy and their propagation in the atmosphere is studied using thermo-hydro-viscous fluid simulation. In third and final step, AGWs interaction with ionosphere is studied using thermo-hydro-magnetic fluid simulation.
[en] Complete text of publication follows. The December 26, 2004 Sumatra-Andaman earthquake (MW 9.3), the fourth largest event (M≥9.0) in the world during the last 100 years, occurred by thrust faulting at the subducting India plate. The main shock rupture, ∼1200 km long and ∼200 km wide, propagated from north of Sumatra to Andaman-Nicobar Islands; the slow rupture generated Tsunami which killed about 300,000 people. The mega thrust event was followed by an intense aftershock activity spreading over the rupture area. Seismotectonic processes suggest predominant thrust faulting in the fore arc region, and normal/strike slip faulting in the back arc region, consistent with the regional tectonics. Pre- and Post- earthquake marine geophysics surveys show changes in magnetic (100 - 150 nT) as well as in bathymetry (15-25 m) of the ocean floor. The transient geomagnetic filed variations and the seismic tomography results are reviewed to shed a new light on the regional seismic structures of the Andaman-Sumatra subduction zone. The sediment filled fore arc basin as well as the volcanic arc is well reflected as high conducting and low seismic velocity zone compared to outer non-volcanic island arc. The high conductivity and low seismic velocity are attributed to conducting magma materials and or trapped fluid due to subduction process, and the images revealed the subducting tectonic features.