scholarly journals The October 9, 1996 earthquake in Cyprus: seismological, macroseismic and strong motion data

1999 ◽  
Vol 42 (1) ◽  
Author(s):  
I. Kalogeras ◽  
G. Stavrakakis ◽  
K. Solomi
Keyword(s):  
Eastern Mediterranean ◽  
Strong Motion ◽  
Strike Slip ◽  
Reverse Fault ◽  
Aftershock Activity ◽  
Motion Data ◽  
Attenuation Relationships ◽  
Largest Aftershock ◽  
Sea Area ◽  
Development Department

On October 9, 1996, an earthquake of magnitude 6.8 occurred in the sea area SW of Cyprus, Eastern Mediterranean. This earthquake, which caused damage mostly in the area of Paphos and Limassol, triggered an accelerograph installed at Yermasoyia dam, north of Limassol. The Geodynamic Institute of the National Observatory of Athens in cooperation with the Geological Survey of Cyprus deployed five digital accelerographs in order to record large aftershocks. Although the aftershock activity lasted over four months and included a large number of earthquakes with magnitudes 4.5 and greater, only the largest aftershock of January 13, 1997, having a magnitude of 5.9, triggered two of these five accelerographs. Moreover another digital accelerograph, operated by the Water Development Department of Cyprus, was triggered and this record was also taken into account in this study. The first Cyprean strong motion records obtained to date, gave us the opportunity to compare the results from their analysis to the already proposed attenuation relationships from other areas of the world with a similar seismotectonic regime. Although a general fitting to the attenuation curves for subduction events and strike-slip/reverse fault events was found, the calculated peak ground accelerations were found to be lower than others. Unfortunately, due to the lack of data from previous Cyprean earthquakes, it was not possible to conclude to precise attenuation

Attenuation Relationships for Shallow Crustal Earthquakes Based on California Strong Motion Data

1997 ◽  
Vol 68 (1) ◽  
pp. 180-189 ◽  
Author(s):  
K. Sadigh ◽  
C.- Y. Chang ◽  
J. A. Egan ◽  
F. Makdisi ◽  
R. R. Youngs
Keyword(s):  
Strong Motion ◽  
Strong Motion Data ◽  
Motion Data ◽  
Attenuation Relationships ◽  
Crustal Earthquakes

Automatic Inversion of Rupture Processes of the Foreshock and Mainshock and Correlation of the Seismicity during the 2019 Ridgecrest Earthquake Sequence

2020 ◽  
Vol 91 (3) ◽  
pp. 1556-1566 ◽  
Author(s):  
Yijun Zhang ◽  
Xujun Zheng ◽  
Qiang Chen ◽  
Xianwen Liu ◽  
Xiaomei Huang ◽  
...  
Keyword(s):  
High Reliability ◽  
Strong Motion ◽  
Temporal Correlation ◽  
Earthquake Sequence ◽  
Coseismic Slip ◽  
Aftershock Activity ◽  
Strong Motion Data ◽  
Motion Data ◽  
Coulomb Failure Stress Change ◽  
Rupture Model

Abstract The 2019 Ridgecrest, California, earthquake sequence included an Mw 6.4 foreshock on 4 July, followed by an Mw 7.1 mainshock about 32 hr later. We determined the rupture patterns of the foreshock and mainshock by applying the automatic iterative deconvolution and stacking method to strong-motion records. The foreshock was characterized by a unilateral rupture toward the southwest, and the shallow portion had a relatively large slip with the maximum value of ∼1.4  m. The mainshock presents an asymmetrical bilateral rupture with an average rupture velocity of 2.0  km/s. More than 80% of the seismic moment was released on the northwest segment of the fault, producing a maximum slip of ∼5.2  m. With the two inferred slip models, we calculated the Coulomb failure stress change (ΔCFS) to analyze the spatial–temporal correlation of the seismicity activity in this sequence. The result shows that the epicenter of the Mw 7.1 mainshock was brought 0.4 bars closer to failure by the Mw 6.4 foreshock, and the stress-increased zone has a good spatial consistence with the coseismic slip distribution of the mainshock and the aftershock distribution of the foreshock. Besides, the positive ΔCFS induced by the mainshock also enhanced its aftershock activity, especially at depths of 4–10 km where the major rupture occurred, inferring that the mainshock-induced ΔCFS may be responsible for the occurrence of aftershocks. In addition, we test the effects of different cutoff frequencies and crust velocity structures on the inversion results. The result reveals that the main source rupture characteristics are almost independent of these factors, implying a high reliability of automation inversion of strong-motion data. Overall, this work indicates that automatic inversion of strong-motion data can provide reliable and rapid rupture model, which is essential for earthquake emergency responses and tsunami early warnings.

Strong Motion Station Characterization and Site Effects during the 1999 Earthquakes in Turkey

2003 ◽  
Vol 19 (3) ◽  
pp. 653-675 ◽  
Author(s):  
Ellen M. Rathje ◽  
Kenneth H. Stokoe ◽  
Brent Rosenblad
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Strong Motion ◽  
Velocity Profiles ◽  
Kocaeli Earthquake ◽  
Amplification Factors ◽  
Motion Data ◽  
Long Period ◽  
Attenuation Relationships

The 1999 Kocaeli and Duzce earthquakes in Turkey generated a moderate amount of strong ground motion data. This paper describes the shear-wave velocity profiles measured at a number of strong motion stations in Turkey using the spectral-analysis-of-surface-waves (SASW) method. The shear-wave velocity profiles from SASW testing compare well with deeper profiles developed by microtremor surface wave inversion, but SASW provides more shear-wave velocity resolution near the ground surface. The developed shear-wave velocity profiles are used to define site classifications for each station. For the Kocaeli earthquake, event-specific attenuation relationships are developed. These relationships show considerable amplification of peak ground acceleration and spectral acceleration (at a period of 0.3 s) at deep soil sites in the far field, but no amplification in the near-fault region. For spectral accelerations at longer spectral periods (1.0 and 2.0 s), amplification is indicated in both the near field and far field. Amplification factors derived from the Kocaeli earthquake strong motion data are generally larger than those used in current attenuation relationships and building codes. The short-period amplification factors derived from the regression decrease with increasing rock motion intensity (PGArock), and the derived long-period amplification factors increase with increasing PGArock. These trends are most likely due to soil nonlinearity. The increase in long-period amplification factors with PGArock is not taken into account in current building codes.

The 2018 Mw 6.8 Zakynthos, Greece, Earthquake: Dominant Strike-Slip Faulting near Subducting Slab

2020 ◽  
Vol 91 (2A) ◽  
pp. 721-732 ◽  
Author(s):  
Efthimios Sokos ◽  
František Gallovič ◽  
Christos P. Evangelidis ◽  
Anna Serpetsidaki ◽  
Vladimír Plicka ◽  
...  
Keyword(s):  
Numerical Models ◽  
Waveform Inversion ◽  
Strong Motion ◽  
Satellite System ◽  
Strike Slip ◽  
Plate Motion ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Motion Data ◽  
Global Navigation Satellite

Abstract With different styles of faulting, the eastern Ionian Sea is an ideal natural laboratory to investigate interactions between adjacent faults during strong earthquakes. The 2018 Mw 6.8 Zakynthos earthquake, well recorded by broadband and strong-motion networks, provides an opportunity to resolve such faulting complexity. Here, we focus on waveform inversion and backprojection of strong-motion data, partly checked by coseismic Global Navigation Satellite System data. We show that the region is under subhorizontal southwest–northeast compression, enabling mixed thrust faulting and strike-slip (SS) faulting. The 2018 mainshock consisted of two fault segments: a low-dip thrust, and a dominant, moderate-dip, right-lateral SS, both in the crust. Slip vectors, oriented to southwest, are consistent with plate motion. The sequence can be explained in terms of trench-orthogonal fractures in the subducting plate and reactivated faults in the upper plate. The 2018 event, and an Mw 6.6 event of 1997, occurred near three localized swarms of 2016 and 2017. Future numerical models of the slab deformation and ocean-bottom seismometer observations may illuminate possible relations among earthquakes, swarms, and fluid paths in the region.

scholarly journals Evaluation of the Strong Ground Motions in the Area Close to the Surface Faults

2018 ◽  
Vol 12 (04) ◽  
pp. 1841002
Author(s):  
Kiyoshi Irie ◽  
Dorjpalam Saruul ◽  
Kazuo Dan ◽  
Haruhiko Torita
Keyword(s):  
Seismic Waves ◽  
Ground Motions ◽  
Strong Motion ◽  
Strike Slip ◽  
Reverse Fault ◽  
Surface Layers ◽  
Period Range ◽  
Strong Ground Motions ◽  
Seismogenic Layer ◽  
Strong Ground

In Japan, the seismic waves radiated from the fault in the surface layers above the seismogenic layer are not considered in the usual strong motion prediction. However, in the inland crustal earthquakes, the strong ground motions in the areas close to the surface faults could be influenced by the seismic waves radiated from the fault in the surface layers. Hence, we evaluated the seismic waves radiated from vertical strike-slip and dipping reverse faults in the surface layers to investigate their influence on the strong motions. The results of the strike-slip fault showed that the seismic waves of the fault normal (FN) component were larger than those of the fault parallel (FP) component in the period range of 0.5–5 s. At least, 80–90% of the FN component was attributed to the seismic wave radiated from the fault in the seismogenic layer. Almost 100% of the FP component was attributed to the seismic waves radiated from the fault in the surface layers. On the other hand, the results of the reverse fault showed that the seismic waves were not attributed to those from the fault in the surface layers.

scholarly journals Geodetic model of the 2015 April 25 Mw 7.8 Gorkha Nepal Earthquake and Mw 7.3 aftershock estimated from InSAR and GPS data

2015 ◽  
Vol 203 (2) ◽  
pp. 896-900 ◽  
Author(s):  
Guangcai Feng ◽  
Zhiwei Li ◽  
Xinjian Shan ◽  
Lei Zhang ◽  
Guohong Zhang ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Strike Slip ◽  
Gps Data ◽  
Reverse Fault ◽  
Lateral Strike Slip ◽  
Nepal Earthquake ◽  
Largest Aftershock ◽  
Total Seismic Moment ◽  
Maximum Thrust ◽  
Seismic Disaster

Abstract We map the complete surface deformation of 2015 Mw 7.8 Gorkha Nepal earthquake and its Mw 7.3 aftershock with two parallel ALOS2 descending ScanSAR paths’ and two ascending Stripmap paths’ images. The coseismic fault-slip model from a combined inversion of InSAR and GPS data reveals that this event is a reverse fault motion, with a slight right-lateral strike-slip component. The maximum thrust-slip and right-lateral strike-slip values are 5.7 and 1.2 m, respectively, located at a depth of 7–15 km, southeast to the epicentre. The total seismic moment 7.55 × 1020 Nm, corresponding to a moment magnitude Mw 7.89, is similar to the seismological estimates. Fault slips of both the main shock and the largest aftershock are absent from the upper thrust shallower than 7 km, indicating that there is a locking lower edge of Himalayan Main Frontal Thrust and future seismic disaster is not unexpected in this area. We also find that the energy released in this earthquake is much less than the accumulated moment deficit over the past seven centuries estimated in previous studies, so the region surrounding Kathmandu is still under the threaten of seismic hazards.

scholarly journals Slip distribution of the 19 September 1985 Michoacan, Mexico, earthquake: Near-source and teleseismic constraints

1989 ◽  
Vol 79 (3) ◽  
pp. 655-669 ◽  
Author(s):  
Carlos Mendoza ◽  
Stephen H. Hartzell
Keyword(s):  
Time Window ◽  
Source Region ◽  
Strong Motion ◽  
Strike Slip ◽  
Inversion Method ◽  
Data Sets ◽  
Aftershock Activity ◽  
Waveform Data ◽  
Simultaneous Inversion ◽  
Mexico Earthquake

Abstract We simultaneously invert the strong-motion velocity records and the long- and intermediate-period teleseismic P waveforms of the 19 September 1985 Michoacan, Mexico, earthquake to recover the distribution of slip on the fault using a point-by-point constrained and stabilized, least-squares inversion method. A fault plane with strike fixed at 300° and dip fixed at 14° is placed in the region of the earthquake hypocenter and divided into 120 subfaults. Rupture is assumed to propagate at a velocity of 2.6 km/sec away from the hypocenter. Synthetic near-source ground motions and teleseismic P waveforms for pure strike-slip and dipslip dislocations are calculated for each subfault. The observed data are then inverted to obtain the amount of strike-slip and dip-slip displacement required of each subfault. We also invert the data sets using a time-window procedure where the subfaults are allowed to slip up to three times. This approach relaxes the constraint of fixed subfault rupture time imposed by a constant rupture velocity. Inversion of the strong-motion data alone yields a slip model similar to the solution previously obtained using only teleseismic waveforms. This result supports the use of teleseismic waveform data for the derivation of fault dislocation models in the absence of strong-motion recordings. Our simultaneous inversion of both data sets suggests that rupture during the Michoacan earthquake was controlled largely by the failure of three major asperities located along the length and down the dip of a 150-km segment of the Cocos-North America plate boundary. The solution contains three major source regions including an 80 km by 55 km source near the hypocenter with a peak slip of 6.5 meters. Two additional sources are present on the southeast portion of the fault about 70 km away from the hypocenter. One of these sources, with a peak slip of 5 meters, covers a 45 km by 60 km area and extends downdip from a depth of about 10 km to 24 km. The third source region is somewhat smaller (30 km by 60 km area, 3.1-meters peak slip) and extends further downdip at depths between 27 km and 39 km. Aftershock activity following the earthquake was associated mainly with the two shallow sources. These two sources are separated by the aftershock zone of the 1981 Playa Azul earthquake.

Processed strong-motion data for the El Salvador earthquake of June 19, 1982

1988 ◽  
Author(s):  
Kenneth W. Campbell ◽  
Sylvester Theodore Algermissen
Keyword(s):  
El Salvador ◽  
Strong Motion ◽  
Strong Motion Data ◽  
Motion Data
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