A Method for Rapid Determination of Moment Magnitude Mw for Moderate to Large Earthquakes from the Near-Field Spectra of Strong-Motion Records (MWSYNTH)

2009 ◽  
Vol 99 (3) ◽  
pp. 1827-1840 ◽  
Author(s):  
B. Delouis ◽  
J. Charlety ◽  
M. Vallee
Keyword(s):  
Rapid Determination ◽  
Near Field ◽  
Strong Motion ◽  
Moment Magnitude ◽  
Strong Motion Records ◽  
Large Earthquakes

Tuning S-Wave Velocity Structure of Deep Sedimentary Layers in the Shimousa Region of the Kanto Basin, Japan, Using Autocorrelation of Strong-Motion Records

2020 ◽  
Vol 110 (6) ◽  
pp. 2882-2891
Author(s):  
Kosuke Chimoto ◽  
Hiroaki Yamanaka
Keyword(s):  
Wave Velocity ◽  
Velocity Structure ◽  
Strong Motion ◽  
S Wave ◽  
Reflected Waves ◽  
Arrival Times ◽  
Strong Motion Records ◽  
Kanto Basin ◽  
Determination Of Parameters

ABSTRACT The autocorrelation of ambient noise is used to capture reflected waves for crustal and sedimentary structures. We applied autocorrelation to strong-motion records to capture the reflected waves from sedimentary layers and used them for tuning the S-wave velocity structure of these layers. Because a sedimentary-layered structure is complicated and generates many reflected waves, it is important to identify the boundary layer from which the waves reflected. We used spectral whitening during autocorrelation analysis to capture the reflected waves from the seismic bedrock with an appropriate smoothing band, which controls the wave arrival from the desired layer boundary. The effect of whitening was confirmed by the undulation frequency observed in the transfer function of the sedimentary layers. After careful determination of parameters for spectral whitening, we applied data processing to the strong-motion records observed at the stations in the Shimousa region of the Kanto Basin, Japan, to estimate the arrival times of the reflected waves. The arrival times of the reflected waves were found to be fast in the northern part of the Shimousa region and slow in the western and southern parts. These arrival times are consistent with those obtained using existing models. Because we observed a slight difference in the arrival times, the autocorrelation function at each station was used for tuning the S-wave velocity structure model of the sedimentary layers using the inversion technique. The tuned models perfectly match the autocorrelation functions in terms of the arrival time of the reflected waves from the seismic bedrock.

Quick determination of earthquake source parameters from GPS measurements: a study of suitability for Taiwan

2019 ◽  
Vol 219 (2) ◽  
pp. 1148-1162
Author(s):  
Jiun-Ting Lin ◽  
Wu-Lung Chang ◽  
Diego Melgar ◽  
Amanda Thomas ◽  
Chi-Yu Chiu
Keyword(s):  
Rapid Determination ◽  
Moment Tensor ◽  
Near Field ◽  
Source Parameters ◽  
Early Warning Systems ◽  
Earthquake Magnitude ◽  
Observation System ◽  
Earthquake Source Parameters ◽  
Finite Fault

SUMMARY We test the feasibility of GPS-based rapid centroid moment tensor (GPS CMT) methods for Taiwan, one of the most earthquake prone areas in the world. In recent years, Taiwan has become a leading developer of seismometer-based earthquake early warning systems, which have successfully been applied to several large events. The rapid determination of earthquake magnitude and focal mechanism, important for a number of rapid response applications, including tsunami warning, is still challenging because of the limitations of near-field inertial recordings. This instrumental issue can be solved by an entirely different observation system: a GPS network. Taiwan is well posed to take advantage of GPS because in the last decade it has developed a very dense network. Thus, in this research, we explore the suitability of the GPS CMT inversion for Taiwan. We retrospectively investigate six moderate to large (Mw6.0 ∼ 7.0) earthquakes and propose a resolution test for our model, we find that the minimum resolvable earthquake magnitude of this system is ∼Mw5.5 (at 5 km depth). Our tests also suggest that the finite fault complexity, often challenging for the near-field methodology, can be ignored under such good station coverage and thus, can provide a fast and robust solution for large earthquake directly from the near field. Our findings help to understand and quantify how the proposed methodology could be implemented in real time and what its contributions could be to the overall earthquake monitoring system.

Moment-magnitude relations based on strong-motion records in Greece

1999 ◽  
Vol 89 (2) ◽  
pp. 442-455 ◽  
Author(s):  
B. N. Margaris ◽  
C. B. Papazachos
Keyword(s):  
Strong Motion ◽  
Soil Classification ◽  
Moment Magnitude ◽  
Systematic Bias ◽  
Local Magnitude ◽  
Strong Motion Data ◽  
Strong Motion Records ◽  
Motion Data ◽  
Input Acceleration ◽  
The Difference

Abstract In this work, the variation of the local magnitude, MLSM, derived from strong-motion records at short distances is examined, in terms of moment magnitude, MW. Strong-motion data from Greek earthquakes are used to determine the strong-motion local magnitude, MLSM, by performing an integration of the equation of motion of the Wood-Anderson (WA) seismograph subjected to an input acceleration. The most reliable strong-motion data are utilized for earthquakes with seismic moments log M0 ≧ 22.0 dyne · cm and calculated local magnitudes, MLSM ≧ 3.7. The correlation between the seismic moments, log M0, and the calculated local magnitudes, MLSM, using strong-motion records is given by log M0 = 1.5*MLSM + 16.07, which is very similar to that proposed by Hanks and Kanamori (1979). Moreover, it is shown that MLSM is equal to moment magnitude, MW, for a large MLSM range (3.9 to 6.6). Comparison of the strong-motion local magnitude and the ML magnitude estimated in Greece (MLGR) and surrounding area shows a systematic bias of 0.4 to 0.5, similar to the difference that has been found between MW and MLGR for the same area. The contribution of the local site effects in the calculation of the local magnitude, MLSM, is also considered by taking into account two indices of soil classification, namely, rock and alluvium or the shear-wave velocity, v30s, of the first 30 m, based on NEHRP (1994) and UBC (1997). An increase of MLSM by 0.16 is observed for alluvium sites. Alternative relations showing the MLSM variation with, v30s are also presented. Finally, examination of the WA amplitude attenuation, −log A0, with distance shows that the Jennings and Kanamori (1983) relation for Δ < 100 km is appropriate for Greece. The same results confirm earlier suggestions that the 0.4 to 0.5 bias between MLGR and MW (also MLSM) should be attributed to a low static magnification (∼800) of the Athens WA instrument on which all other ML relations in Greece have been calibrated.

scholarly journals Rapid determination of the photometric bidirectional scatter distribution function by use of a near-field goniophotometer

2014 ◽  
Author(s):  
Frédéric B. Leloup ◽  
Ward De Ketelaere ◽  
Jan Audenaert ◽  
Peter Hanselaer
Keyword(s):  
Distribution Function ◽  
Rapid Determination ◽  
Near Field

Simulating strong motions of large earthquakes using recordings of small earthquakes: the Loma Prieta mainshock as a test case

1995 ◽  
Vol 85 (4) ◽  
pp. 1144-1160
Author(s):  
Arthur Frankel
Keyword(s):  
Stress Drop ◽  
Site Response ◽  
Strong Motion ◽  
Site Effect ◽  
Corner Frequency ◽  
Simple Method ◽  
Strong Motion Records ◽  
Loma Prieta Earthquake ◽  
Loma Prieta ◽  
Large Earthquakes

Abstract A simple method is developed for predicting ground motions for future large earthquakes for specific sites by summing and filtering recordings of adjacent small earthquakes. This method is tested by simulating strong-motion records for the Loma Prieta earthquake (M 7.0) using aftershocks (M 3.7 to 4.0) recorded at the same sites. I use an asperity rupture model where the rms stress drop averaged over the fault plane is constant with moment. The observed spectra indicate that stress drop remains constant from the M 3 aftershocks up to the M 7 mainshock, about six orders of magnitude in seismic moment. Each simulation sums the seismogram of one aftershock with time delays appropriate for propagating rupture and incorporates directivity and site response. The simulation scales the spectrum in accordance with a constant stress drop, ω−2 source model. In this procedure, the high-frequency energy of the aftershock sum above the corner frequency of the aftershock is not reduced when it is convolved with the mainshock slip velocity function, unlike most previous methods of summation. For most cases, the spectra (0.6 to 20 Hz), peak accelerations, and durations of the simulated mainshock records are in good agreement with the observed strong-motion records, even though only one aftershock waveform was used in each simulation. This agreement indicates that the response of these soil sites is essentially linear for accelerations up to about 0.3 g. The summed aftershock records display the same site-dependent values of fmax as the mainshock records, implying that fmax is a site effect rather than a property of the mainshock rupture process.

Magnitude Calculation without Saturation from Strong-Motion Waveforms

2020 ◽  
Author(s):  
Zhang Hongcai ◽  
Diego Melgar ◽  
Dara E. Goldberg
Keyword(s):  
Real Time ◽  
Near Field ◽  
Magnitude Estimate ◽  
Strong Motion ◽  
Global Navigation Satellite Systems ◽  
Coseismic Deformation ◽  
Ground Displacement ◽  
Strong Motion Records ◽  
Satellite Systems ◽  
Global Navigation Satellite

ABSTRACT After destructive earthquakes, it is a challenge to estimate magnitude rapidly and accurately for dissemination to emergency responders and the public. Here, we propose criteria to calculate peak ground displacement (PGD) from strong-motion records, which can be used to calculate unsaturated event magnitude. Using collocated strong-motion and Global Navigation Satellite Systems observations of five major earthquakes in Japan, we demonstrate the effectiveness and accuracy of our strategy. Our results show that, with the right filtering criteria, PGD estimated from strong-motion acceleration waveforms is consistent with geodetic estimates. The methodology, however, does not allow for calculation of reliable estimates of coseismic deformation or other ground displacement metrics. We demonstrate a simulated real-time magnitude estimation that suggests it is feasible to generate an unsaturated magnitude estimate in real time from near-field strong-motion records. These findings have important implications for early warning and emergency response in seismically active areas, especially where real-time strong-motion data are more widely available than geodetic measurements.

scholarly journals Effect of distance on local magnitudes found from strong-motion records

1983 ◽  
Vol 73 (1) ◽  
pp. 265-280
Author(s):  
Paul C. Jennings ◽  
Hiroo Kanamori
Keyword(s):  
Near Field ◽  
Strong Motion ◽  
Similar Data ◽  
Attenuation Curve ◽  
Imperial Valley ◽  
Strong Motion Records ◽  
Motion Data ◽  
San Fernando ◽  
Numerous Data ◽  
A Site

abstract Values of local magnitude ML, are calculated from 56 strong-motion accelerograms recorded in the Imperial Valley earthquake of 15 October 1979 according to procedures developed earlier (Kanamori and Jennings, 1978). These data, plus similar data from the San Fernando earthquake of 9 February 1971 and additional, less numerous data from several other California earthquakes, are used to investigate the use of different measures of distance in near-field determinations of ML: this investigation has relevance for similar uses of distances in determining seismic design criteria. In addition, the consistency of the values of ML found from the strong-motion data is examined from the viewpoint of assessing the need for any correction in the standard attenuation curve, −log10A0(Δ). It was found that the most consistent values of ML result when distance is measured to the closest point on the surface trace of the fault if a site lies within a circle with diameter equal to the extent of faulting and centered on the center of faulting (center of energy release). Outside this circle, the distance measured to the center of the circle is recommended. A consistent trend in the values of ML found from strong-motion records is seen in the data. The values start, at zero distance, at essentially the far-field value and then decrease to −1/4 unit at about 20 km. Then they rise to +1/4 unit at 50 to 60 km. A smooth revision to the standard attenuation curve is presented which removes this systematic trend.

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