Ting Li Lin

Magnitude estimation using the covered areas of strong ground motion in earthquake early warning

[1] We collected the strong-motion accelerograms with peak ground acceleration (PGA) larger than 100 Gal (1 Gal = 1.0 cm/s 2 ) from large crustal earthquakes in Taiwan recorded by the Taiwan Strong Motion Instrumentation Program (TSMIP) stations to find an empirical relationship between the area of high PGA and the corresponding earthquake magnitude. We found that the logarithms of the areas inside the PGA contours have a linear relation to the corresponding earthquake magnitudes. We propose that this relationship might be able to rapidly define the earthquake magnitude while providing sufficient seismic station coverage and might have practical application in earthquake early warning (EEW) and rapid reporting systems. The proposed magnitude estimation method is directly related to the level of strong surface shaking and is inherently suitable for the purpose of the EEW and rapid reporting systems.

A Fast Magnitude Estimation for the 2011 Mw 9.0 Great Tohoku Earthquake

After the occurrence of a large earthquake, rapid reporting is useful and necessary for resource dispatch management and quick damage assessment. In practice, a ground-motion prediction or a shaking-intensity estimation can be realized once the location and magnitude of an earthquake become available. Rapid availability of event information can also fulfill inquiries and alleviate the misgivings of the public and media. Using the traditional travel-time method, rapid earthquake location is a simple task once a few P -wave arrivals are known. In contrast, a quick and accurate estimate of earthquake magnitude is a nontrivial problem, especially for an extremely large regional event. For a teleseismic-determined moment magnitude, it may take tens of minutes for the propagation of teleseismic waves. For a method using first-arrival P waveforms of broadband seismograms for moment magnitude determinations (Tsuboi et al. , 1995, 1999), the reporting time for moderate-sized earthquakes still takes several minutes. In addition, common high-gain broadband stations will suffer a severe amplitude-clipping problem from regional large earthquakes. The M w 9.0 (Global Centroid Moment Tensor [CMT]) Tohoku-Chiho Taiheiyo-Oki (Tohoku) earthquake that occurred on 11 March 2011 was unprecedented in size since Japan started modern instrumental recordings 130 years ago. The megathrust Tohoku earthquake ruptured the Pacific–North American (Okhotsk) plate boundary off the Pacific coast of northeastern Japan. The work presented here employed the empirical method of Wu and Teng (2004) for quick M w determinations of crustal earthquakes in Japan using time integration over the strong-shaking duration for absolute values of acceleration records. In the study of Wu and Teng (2004), the maximum magnitude was for the 1999 M w 7.6 (Global CMT) Chi-Chi earthquake in Taiwan. In this work, the largest event was the 2011 M w 9.0 Tohoku earthquake in Japan. We show that the method of Wu and …

Application of τc*Pd in earthquake early warning

Rapid assessment of damage potential and size of an earthquake at the station is highly demanded for onsite earthquake early warning. We study the application of τc*Pd for its estimation on the earthquake size using 123 events recorded by the borehole stations of KiK-net in Japan. The new type of earthquake size determined by τc*Pd is more related to the damage potential. We find that τc*Pd provides another parameter to measure the size of earthquake and the threshold to warn strong ground motion.

Application of Taiwan borehole seismometers in 1 earthquake early warning

Earthquake early warning (EEW) is an effective approach to mitigating earthquake damage. This is the first study evaluating borehole seismograph application to EEW in Taiwan. We selected inland and offshore earthquakes with ML larger than 4.0 occurring between 2012 and 2014 for this study. We investigated the Pd attenuation relationship as a function of the hypocentral distance (R) and magnitude (M). The new Pd attenuation relationship specific for the borehole records is expressed as: log(Pd) = 0.689ML 0.741log(R) 4.608 ± 0.248. Once the earthquake location is determined, this regression equation is used to quickly estimate Pd magnitude (MPd). According to the new regression equation formulated specifically for borehole observations in Taiwan, our result shows that the standard MPd deviation is about 0.21 relative to ML. This smaller standard deviation of 0.21 compared to that of the free-surface records might be attributed to the reduced influence of near-surface effects in the borehole records. We propose a new robust Pd regression equation for the Taiwan borehole seismic network.

Source Uncertainty Estimation in Seismic Intensity Determination of the Taiwan Region

In this work, we quantify the effect of source uncertainties, other than earthquake magnitude and location, in rapid seismic intensity determinations in Taiwan using the strong‐motion accelerograms recorded by stations of the Taiwan Strong‐Motion Instrumentation Program (TSMIP) between 1991 and 2010. We find that rapid earthquake reporting assumes that a point source has an uncertainty of 0.5° in intensity and 7.2  cm/s2 in peak ground acceleration (PGA). Therefore, these values can be regarded as the upper bound for precision in the Taiwan rapid reporting system (RRS).