Effect of Finite Frequency Bandwidth Limitation on Evaluations of Seismic Radiation Energy of the 1999 Chi-Chi Earthquake

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This paper reviews studies on earthquake energies, seismic efficiency, radiation efficiency, scaled energy and energy-magnitude law conducted by Taiwan seismologists and foreigners who used seismic data from Taiwan to study these problems. Sufficient seismic and geodetic data permits energy measurements from the 20 September 1999 M s 7.6 Chi-Chi earthquake and its larger-sized aftershocks. The results provide significant information on earthquake physics. The issues in this review paper include measures of these physical quantities and related theoretical or analytical studies of these physical quantities made by both Taiwan's seismologists and foreigners who used seismic data of Taiwan to study related problems.

Section: The Effect Due To Finite Frequency Bandwidth Limitationsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: The Effect Due To Finite Frequency Bandwidth Limitationmentioning

confidence: 99%

“…The variations in E s3 '/E s with f l /f c (from 0.05 -0.95) for ten values for f u /f c (from 2 -20). The dotted line represents E s3 '/E s =1 (afterWang and Huang 2007).…”

mentioning

confidence: 99%

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Studies of Earthquake Energies in Taiwan: A Review

Wang

2016

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“…Hwang et al (2001) mea sured the val ues of E s , M o , and E s /M o of the mainshock from near-fault seis mic data. Wang (2004) and Wang and Huang (2007) cor rected their value of E s to re move the ef fect of fi nite fre quency band width lim i ta tion. Huang et al (2002) mea sured the scaled en er gies for two larger-sized after shocks from lo cal seismograms.…”

Section: Introductionmentioning

confidence: 99%

Scaled Energies of ML > 5.1 After shocks of the 1999 Chi-Chi, Taiwan, Earthquake Measured from Local Seismograms

Huang¹

2009

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In this study, we mea sure the seis mic ra di a tion en ergy, E s , and seis mic mo ment, M o , of twenty-two larger-sized after shocks with 5.1 £ M L £ 6.5 of the 1999 M s 7.6 Chi-Chi, Tai wan, earth quake from high-qual ity dig i tal strong-mo tion data re corded at sta tions with epicentral dis tances of less than 50 km through a method pro posed by An drews (1986 . The scaled en er gies of the 22 events are de pend ent upon earth quake mag ni tude, M s , when both E s and M o are eval u ated from lo cal seismograms; yet, in de pend ent of M s when M o is es ti mated from teleseismic data. Scaled en ergy slightly de pends on the depth, h (in km), through the fol low ing form:. In ad di tion, the cor ner fre quency, f c , is also mea sured. Its value ranges from 0.15 to 1.34. The scal ing law be tween M o and f c is:Key words: Scaled en ergy, Ra di a tion en ergy, Seis mic mo ment, After shocks, Chi-Chi earth quake Sci., 20, 671-685, doi: 10.3319/TAO.2008.10.13.01(T) IN TRO DUC TIONThe seis mic-wave en ergy, E s , and seis mic mo ment, M o , are two com monly used pa ram e ters quan ti fy ing earth quakes and can be di rectly mea sured from seismograms. The scaled en ergy, E s /M o , which is de fined to be the ra tio of seis mic radiation en ergy to seis mic mo ment, de notes the ra di ated energy per unit seis mic mo ment of an earth quake. Sev eral fac tors could af fect the mea sures of E s and M o from lo cal, regional, and teleseismic data, thus, re sult ing in high divergence of E s /M o (Vassiliou and Kanamori 1982;Kikuchi and Fukao 1988;Choy and Boatwright 1995). Gen er ally, E s mea sured from lo cal seismograms is larger than that done from teleseismic data (Bolt 1986;Smith et al. 1991;Singh and Ordaz 1994;Hwang et al. 2001;Huang et al. 2002). The strong site ef fect at higher fre quen cies (greater than 0.01 Hz) can pro duce an over es ti ma tion of source parameters (Boatwright et al. 2002; Pérez-Campes et al. 2003) while fi nite fre quency band width lim i ta tion leads to an oppo site ef fect (Hwang et al. 2001;Ide and Beroza 2001;Wang 2004). Boore (1988), Di Bona and Rovelli (1988), and Singh and Ordaz (1994 stressed that E s can be un deres ti mated when high-fre quency sig nals are not in cluded. On the other hand, the es ti mate of M o from long-pe riod tele seismic data has lower un cer tainty due to the use of longer-pe riod sig nals.Kanamori ( . They also stressed that dur ing an earth quake rup ture en ergy loss due to co he sion can not be ig nored. Brodsky and Kanamori (2001)

Source Parameters of the 2005 Mw 7.2 Miyagi-Oki, Japan, Earthquake as Inferred from Teleseismic P-Waves

Hwang¹,

Lin²,

Yu³

et al. 2010

We investigate the fault parameters of the 2005 Miyagi-Oki (Japan) earthquake using duration variations of teleseismic P-waves. The results show that the earthquake has a thrust-type mechanism and a seismic moment of 4.46 × 10 19 Nm. Rupture directivity analysis suggests that the earthquake occurred as a result of a bilateral faulting on the fault plane with a strike of 247°, a dip of 17° and a slip of 125°. The optimal rupture azimuth, measured counterclockwise from the strike on the fault plane, is 170° (or 350°). The rupture length and average source duration are estimated to be 73.4 km and 14.5 sec, respectively. Thus the rupture velocity is 2.53 km sec -1 (~0.57 times the value of S-wave velocity), which is lower than the value for other similarly sized earthquakes. This implies that the 2005 Miyagi-Oki earthquake was probably a slow event. Consequently, there may have been less release of high-frequency seismic energy, leading to lower radiated seismic energy and radiation efficiency (~0.32 -0.48). In other words, relatively larger fracture energy occurred during earthquake faulting in addition to the heat due to friction. The ratio of the static stress drop to the apparent stress (> 2.0) also suggests that the earthquake can be modeled as a frictional overshoot in a stress model, which implies the transformation of a lower percentage of strain energy into seismic-wave energy during the process of earthquake rupturing.