Pre-seismic ionospheric anomalies detected before the 2016 Taiwan earthquake

On Feb. 5 2016 (UTC), an earthquake with moment magnitude 6.4 occurred in southern Taiwan, known as the 2016 (Southern) Taiwan earthquake. In this study, evidences of seismic earthquake precursors for this earthquake event are investigated. Results show that ionospheric anomalies in Total Electric Content (TEC) can be observed before the earthquake. These anomalies were obtained by processing TEC data, where such TEC data are calculated from phase delays of signals observed at densely arranged ground-based stations in Taiwan for Global Navigation Satellite Systems. This shows that such anomalies were detected within 1 hour before the event

Global Seismic Nowcasting With Shannon Information Entropy.

Seismic nowcasting uses counts of small earthquakes as proxy data to estimate the current dynamical state of an earthquake fault system. The result is an earthquake potential score that characterizes the current state of progress of a defined geographic region through its nominal earthquake "cycle." The count of small earthquakes since the last large earthquake is the natural time that has elapsed since the last large earthquake (Varotsos et al., 2006, https://doi.org/10.1103/PhysRevE.74.021123). In addition to natural time, earthquake sequences can also be analyzed using Shannon information entropy ("information"), an idea that was pioneered by Shannon (1948, https://doi.org/10.1002/j.1538-7305.1948.tb01338.x). As a first step to add seismic information entropy into the nowcasting method, we incorporate magnitude information into the natural time counts by using event self-information. We find in this first application of seismic information entropy that the earthquake potential score values are similar to the values using only natural time. However, other characteristics of earthquake sequences, including the interevent time intervals, or the departure of higher magnitude events from the magnitude-frequency scaling line, may contain additional information

Retrospective Evaluation of the Five-Year and Ten-Year CSEP-Italy Earthquake Forecasts

On 1 August 2009, the global Collaboratory for the Study of Earthquake Predictability (CSEP) launched a prospective and comparative earthquake predictability experiment in Italy. The goal of the CSEP-Italy experiment is to test earthquake occurrence hypotheses that have been formalized as probabilistic earthquake forecasts over temporal scales that range from days to years. In the first round of forecast submissions, members of the CSEP-Italy Working Group presented eighteen five-year and ten-year earthquake forecasts to the European CSEP Testing Center at ETH Zurich. We considered the twelve time-independent earthquake forecasts among this set and evaluated them with respect to past seismicity data from two Italian earthquake catalogs. In this article, we present the results of tests that measure the consistency of the forecasts with the past observations. Besides being an evaluation of the submitted time-independent forecasts, this exercise provided insight into a number of important issues in predictability experiments with regard to the specification of the forecasts, the performance of the tests, and the trade-off between the robustness of results and experiment duration. We conclude with suggestions for the future design of earthquake predictability experiments.Comment: 43 pages, 8 figures, 4 table

Rupture process of the recent large Sumatra earthquakes: 26/12/2004 (Mw=9.3) and 28/03/2005 (Mw=8.6)

The Sumatra mega-earthquake with magnitude 9.3 of 26 December 2004 was the strongest earthquake in the world since the 1964 Alaska earthquake and the fourth since 1900. The earthquake occurred on the interface of the India and Burma plates and triggered a massive tsunami that affected several countries throughout South and Southeast Asia. The rupture, estimated by the aftershock distribution, start from central Sumatra northward for about 1200 kilometres (Borges et al., 2004). Three months latter in 28 March 2005, about 200 km south of this event, but at a greater depth (28 km) occurred a magnitude 8.6 earthquake. This event was probably triggered by stress variations caused by the December Sumatra mega-earthquake (McCloskey et al., 2005). In this work we describe the rupture process of the both earthquakes estimated from teleseismic broad-band waveform data

Virtual Reality of Earthquake Ground Motions for Emergency Response

Ground motions interface earthquake science and engineering to advance understanding of seismic hazards and risk. Virtual reality provides an attractive tool to extend knowledge of the research community to a larger audience. This work visualizes emergency response under extreme motions, in the CAVE of the MARquette Visualization Laboratory. The visualization (a) displays ground motions (from the science community), (b) inputs these motions to structural models (from the engineering community) and illustrates the resulting responses, (c) translates structural responses to damage states of building elements, (d) creates a virtual room subjected to the perception associated with such earthquake shaking, and (e) introduces the human element of emergency response in this immersive environment. Building upon previous work on earthquake simulations, performance-based earthquake engineering (PBEE), building information modeling (BIM), and earthquake awareness, this study integrates elements of PBEE and BIM within the CAVE environment to provide visual information for decision making. Real-time or near real-time information via earthquake early warning (EEW) and structural health monitoring (SHM) further facilitates response within a limited time frame. As advanced technologies contribute to the future of community resilience, visualization plays an emerging role in connecting earthquake science, engineering, and policy

Analyses of strong motion earthquake accelerograms, Volume IV - Fourier amplitude spectra; Parts Q, R and S - Accelerograms IIQ233 to IIQ243, IIR244 to IIR254, IIS255 to IIS273

The corrected records analyzed in this report, Volume IV, Parts Q, R, and S, appeared in Volume II, Parts Q and R, Report No. EERL 74-56, and Volume II, Part S, Report No. EERL 74-57. Their uncorrected versions were published in Volume I, Part Q, Report No. EERL 73-22; Volume I, Part R, Report No. EERL 73-23; and Volume I, Part S, Report No. EERL 73-24

Importance of small earthquakes for stress transfers and earthquake triggering

We estimate the relative importance of small and large earthquakes for static stress changes and for earthquake triggering, assuming that earthquakes are triggered by static stress changes and that earthquakes are located on a fractal network of dimension D. This model predicts that both the number of events triggered by an earthquake of magnitude m and the stress change induced by this earthquake at the location of other earthquakes increase with m as \~10^(Dm/2). The stronger the spatial clustering, the larger the influence of small earthquakes on stress changes at the location of a future event as well as earthquake triggering. If earthquake magnitudes follow the Gutenberg-Richter law with b>D/2, small earthquakes collectively dominate stress transfer and earthquake triggering, because their greater frequency overcomes their smaller individual triggering potential. Using a Southern-California catalog, we observe that the rate of seismicity triggered by an earthquake of magnitude m increases with m as 10^(alpha m), where alpha=1.00+-0.05. We also find that the magnitude distribution of triggered earthquakes is independent of the triggering earthquake magnitude m. When alpha=b, small earthquakes are roughly as important to earthquake triggering as larger ones. We evaluate the fractal correlation dimension of hypocenters D=2 using two relocated catalogs for Southern California, and removing the effect of short-term clustering. Thus D=2alpha as predicted by assuming that earthquake triggering is due to static stress. The value D=2 implies that small earthquakes are as important as larger ones for stress transfers between earthquakes.Comment: 14 pages, 7 eps figures, latex. In press in J. Geophys. Re