scholarly journals Historical seismicity and rates of crustal deformation along the margins of the Ordos block, north China

1984 ◽  
Vol 74 (5) ◽  
pp. 1767-1783
Author(s):  
S. G. Wesnousky ◽  
L. M. Jones ◽  
C. H. Scholz ◽  
Qidong Deng
Keyword(s):  
Crustal Deformation ◽  
Seismic Moment ◽  
Historical Earthquakes ◽  
Historical Record ◽  
Lateral Shear ◽  
Fault Systems ◽  
Ordos Block ◽  
Earthquakes In China ◽  
Large Earthquakes ◽  
Southern Ningxia

Abstract Earthquakes in China show an empirical relation between seismic moment (M0) and the areal distribution of Modified Mercalli intensities VI and VIII (log M0 = 16.66 + 0.91 log AVIII and log M0 = 14.35 + 1.16 log AVI, where A and M0 are measured in squared kilometers and Newton-meter, respectively). The empirical relations may be used to estimate M0 for historical earthquakes in China to within a factor of three, on average, when sufficient isoseismal data exist. This observation and an extensive collection of isoseismal maps are used to estimate M0 for large earthquakes that occurred along the margins of the Ordos block during the last 700 yr. Focal parameters of the historical events are inferred from the orientation and displacements across Quaternary faults. Average rates of crustal deformation are then estimated from the 700-yr historical record with formulas that relate the occurrence rate of seismic moment in a region to rates of crustal strain. The Shanxi and northern Ningxia graben systems are situated along the eastern and northwestern edges of the Ordos block, respectively. Normal faults in the two systems trend northeasterly and are characterized by a component of right-lateral slip. The deformation resulting from slip during earthquakes in each of the respective fault systems is estimated at about 0.5 to 1.0 mm/yr of both right-lateral shear and north by northwest extension. The Weihe graben system bounds the southern edge of the Ordos block, strikes easterly and conjugate to the Shanxi and northern Ningxia fault systems, and exhibits left-lateral normal fault displacements. The average rate of deformation across Weihe is described by about 1.0 mm/yr of north by northwest extension and 1.5 mm/yr left-lateral east-west shear. The Hetao fault system delineates the northern edge of the Ordos block and displays Quaternary faults similar in orientation and mechanism to that observed in Weihe. Although mapped faults in Hetao exhibit evidence of Quaternary displacement, crustal deformation rates are not estimated because there exists no historical record of large earthquakes in the area. In southern Ningxia, at the southwest boundary of the Ordos block, deformation occurs by slip on left-lateral strike-slip faults oriented in an easterly azimuth and thrust faults with strikes ranging from southeast to south. The average deformation rate in southern Ningxia is found to be about 4.0 mm/yr of east by northeast contraction and 10.0 mm/yr of left-lateral shear. Deformation of each of the fault systems is consistent with a regional compressive stress that trends northeast and results in an average of about 3.0 mm/yr each of contraction at N70°E and extension of N160°E across the entire region. Inasmuch as uncertainties in estimates of M0 for historical earthquakes are about a factor of three, a similar uncertainty is attached to rates of crustal strain determined in this manner.

scholarly journals A large unknown historical earthquake in the Abruzzi region (Central Italy): combination of geological and historical data

1995 ◽  
Vol 38 (5-6) ◽  
Author(s):  
G. D'Addezio ◽  
F. R. Cinti ◽  
D. Pantosti
Keyword(s):  
Historical Data ◽  
Central Italy ◽  
Large Earthquake ◽  
Historical Earthquakes ◽  
Historical Record ◽  
Historical Earthquake ◽  
Recent Event ◽  
Complete Knowledge ◽  
Historical Investigation

The combination of paleoseismological and historical investigation can be used to obtain a complete knowledge of past earthquakes. In Italy the 1000 year-long record of historical earthquakes provides an opportunity to compare data from the catalogue with results from paleoseismologic investigations. Trenching results along the Ovindoli-Pezza Fault (OPF). in the Abruzzi region. showed two surface faulting events. The most recent of these events occurred after 1019 A.D. and should be reported in the Catalogue of Italian Seismicity. Nevertheless, the earthquake appears to be missed or not well located in the Catalogue. In order to define in which century a large earthquake on the OPF should have clearly left a sign in the historical record, we carried out historical investigations back to the XI century. The studies were mainly focu5ed on disclosing possible <<negative>> e vidence for the occurrence of the most recent event along the OPF. No clear records related to this event were found but on the basis of the information we obtained the occurrence of this earthquake can be constrained between 1019 A.D. and the XV century. possibly between 1019 A.D. and XIII century.

Multisegment Rupture Hazard Modeling along the Xianshuihe Fault Zone, Southeastern Tibetan Plateau

2020 ◽  
Author(s):  
Jia Cheng ◽  
Thomas Chartier ◽  
Xiwei Xu
Keyword(s):  
Slip Rate ◽  
Historical Earthquakes ◽  
Input Constraints ◽  
Ground Acceleration ◽  
Slip Rates ◽  
Fault Slip Rates ◽  
Seismicity Rates ◽  
Xianshuihe Fault Zone ◽  
Large Earthquakes ◽  
Southern Section

Abstract The Xianshuihe fault is a remarkable strike-slip fault characterized by high slip rate (∼10  mm/yr) and frequent strong historical earthquakes. The potential for future large earthquakes on this fault is enhanced by the 2008 Mw 7.9 Wenchuan earthquake. Previous works gave little attention to the probabilities of multisegment ruptures on the Xianshuihe fault. In this study, we build five possible multisegment rupture combination models for the Xianshuihe fault. The fault slip rates and historical earthquakes are used as input constraints to model the future seismicity on the fault segments and test whether the rupture combination models are appropriate. The segment combination model, based essentially on historical ruptures, has produced the seismicity rates most consistent with the historical records, although the model with ruptures on both the entire northern section and southern section should also be considered. The peak ground acceleration values with a return period of 475 yr calculated using the modeled rates on the Xianshuihe fault for both two models are on average larger than the values of the China Seismic Ground Motion Parameters Zonation Map.

Implementation of Sugeno: ANFIS for forecasting the seismic moment of large earthquakes over Indo-Himalayan region

2017 ◽  
Vol 90 (1) ◽  
pp. 391-405 ◽  
Author(s):  
Sutapa Chaudhuri ◽  
Arumita Roy Chowdhury ◽  
Payel Das
Keyword(s):  
Seismic Moment ◽  
Himalayan Region ◽  
Large Earthquakes

Magnitudes of future large earthquakes near Istanbul quantified from 1500 years of historical earthquakes, present-day microseismicity and GPS slip rates

2019 ◽  
Vol 764 ◽  
pp. 77-87 ◽  
Author(s):  
Fatih Bulut ◽  
Bahadır Aktuğ ◽  
Cenk Yaltırak ◽  
Aslı Doğru ◽  
Haluk Özener
Keyword(s):  
Historical Earthquakes ◽  
Slip Rates ◽  
Large Earthquakes

scholarly journals Historical and paleo-tsunami deposits on Kamchatka, Russia: long-term chronologies and long-distance correlations

2001 ◽  
Vol 1 (4) ◽  
pp. 177-185 ◽  
Author(s):  
T. K. Pinegina ◽  
J. Bourgeois
Keyword(s):  
Volcanic Ash ◽  
Average Frequency ◽  
Historical Record ◽  
Eastern Coast ◽  
Tsunami Deposits ◽  
Long Distance ◽  
Proxy Record ◽  
Millennial Time Scale ◽  
Large Earthquakes

Abstract. Along the eastern coast of Kamchatka, at a number of localities, we have identified and attempted to assign ages to deposits of both historic and prehistoric (paleo-) tsunamis. These deposits are dated and correlated using tephrochronology from Holocene marker tephra and local volcanic ash layers. Because the historical record of earthquakes and tsunamis on Kamchatka is so short, these investigations can make important contributions to evaluating tsunami hazards. Moreover, because even the historical record is spotty, our work helps add to and evaluate tsunami catalogues for Kamchatka. Furthermore, tsunami deposits provide a proxy record for large earthquakes and thus are important paleoseismological tools. The combined, preserved record of tsunami deposits and of numerous marker tephra on Kamchatka offers an unprecedented opportunity to study tsunami frequency. Using combined stratigraphic sections, we can examine both the average frequency of events for each locality, and also changes in frequency through time. Moreover, using key marker tephra as time lines, we can compare tsunami frequency and intensity records along the Kamchatka subduction zone. Preliminary results suggest real variations in frequency on a millennial time scale, with the period from about 0 to 1000 A.D. being particularly active at some localities.

EnKF estimation of the viscoelastic deformation and the viscosity

2020 ◽  
Author(s):  
Makiko Ohtani
Keyword(s):  
Data Assimilation ◽  
Crustal Deformation ◽  
Surface Deformation ◽  
Synthetic Data ◽  
Ground Surface ◽  
Inelastic Strain ◽  
Large Earthquake ◽  
Forward Model ◽  
Viscoelastic Deformation ◽  
Large Earthquakes

&lt;p&gt;Following large earthquakes, postseismic crustal deformations are often observed for more than years. They include the afterslip and the viscoelastic deformation of the crust and the upper mantle, activated by the coseismic stress change. The viscoelastic deformation gives the stress change on the neighboring faults, hence affects the seismic activity of the surrounding area, for a long period after the large earthquake. So, estimating the viscoelastic deformation after the large earthquakes is important.&lt;/p&gt;&lt;p&gt;In order to estimate the time evolution of the viscoelastic deformation after a large earthquake, we also need to know the viscoelastic structure around the area. Recently, the Ensemble Kalman filter method (EnKF), a sequential data assimilation method, starts to be used for the crustal deformation data to estimate the physical variables (van Dinther et al., 2019, Hirahara and Nishikiori, 2019). With data assimilation, we get a more provable estimation by combining the data and the time-forward model than only using the data. Hirahara and Nishikiori (2019) used synthetic data and showed that EnKF could effectively estimate the frictional parameters on the SSE (slow slip event) fault, addition to the slip velocity. In the present study, I applied EnKF to estimate the viscosity and the inelastic strain after a large earthquake, both the physical property and the variables.&lt;/p&gt;&lt;p&gt;First, I constructed the forward model simulating the evolution of the viscoelastic deformation, following the equivalent body force method (Barbot and Fialko, 2010; Barbot et al., 2017). This method is appropriate for applying EnKF, because the ground surface deformation rate is represented by the inelastic strain at the moment, and the history of the strain is not required. Then, we applied EnKF based on the forward model and executed some numerical experiments using a synthetic postseismic crustal deformation data.&lt;/p&gt;&lt;p&gt;In this presentation, I show the result of a simple setting. I assumed the medium to be two layers with a homogeneous viscoelastic region underlying an elastic region. The synthetic data is made by giving a slip on a fault at time &lt;em&gt;t&lt;/em&gt; = 0 and simulating the time evolution of the ground surface deformation. For assimilation, I assumed that the slip on the fault and the stress distribution just after the large earthquake is known. Then we executed the assimilation every 30 days after the large earthquake. I found that I can get a good estimation of the viscosity after &lt;em&gt;t&lt;/em&gt; &gt; 150 days.&lt;/p&gt;

Real-time monitoring of seismic moment and radiated energy

2020 ◽  
Author(s):  
Davide Scafidi ◽  
Daniele Spallarossa ◽  
Matteo Picozzi ◽  
Dino Bindi
Keyword(s):  
Real Time ◽  
Seismic Moment ◽  
P Wave ◽  
Calibration Data ◽  
S Wave ◽  
Data Set ◽  
Local Networks ◽  
Radiated Energy ◽  
The Impact ◽  
Large Earthquakes

&lt;p&gt;Understanding the dynamics of faulting is a crucial target in earthquake source physics (Yoo et al., 2010). To study earthquake dynamics it is indeed necessary to look at the source complexity from different perspectives; in this regard, useful information is provided by the seismic moment (M0), which is a static measure of the earthquake size, and the seismic radiated energy (ER), which is connected to the rupture kinematics and dynamics (e.g. Bormann &amp; Di Giacomo 2011a). Studying spatial and temporal evolution of scaling relations between scaled energy (i.e., e = ER/M0) versus the static measure of source dimension (M0) can provide valuable indications for understanding the earthquake generation processes, single out precursors of stress concentrations, foreshocks and the nucleation of large earthquakes (Picozzi et al., 2019). In the last ten years, seismology has undergone a terrific development. Evolution in data telemetry opened the new research field of real-time seismology (Kanamori 2005), which targets are the rapid determination of earthquake location and size, the timely implementation of emergency plans and, under favourable conditions, earthquake early warning. On the other hand, the availability of denser and high quality seismic networks deployed near faults made possible to observe very large numbers of micro-to-small earthquakes, which is pushing the seismological community to look for novel big data analysis strategies. Large earthquakes in Italy have the peculiar characteristic of being followed within seconds to months by large aftershocks of magnitude similar to the initial quake or even larger, demonstrating the complexity of the Apennines&amp;#8217; faults system (Gentili and Giovanbattista, 2017). Picozzi et al. (2017) estimated the radiated seismic energy and seismic moment from P-wave signals for almost forty earthquakes with the largest magnitude of the 2016-2017 Central Italy seismic sequence. Focusing on S-wave signals recorded by local networks, Bindi et al. (2018) analysed more than 1400 earthquakes in the magnitude ranges 2.5 &amp;#8804; Mw &amp;#8804; 6.5 of the same region occurred from 2008 to 2017 and estimated both ER and M0, from which were derived the energy magnitude (Me) and Mw for investigating the impact of different magnitude scales on the aleatory variability associated with ground motion prediction equations. In this work, exploiting first steps made in this direction by Picozzi et al. (2017) and Bindi et al. (2018), we derived a novel approach for the real-time, robust estimation of seismic moment and radiated energy of small to large magnitude earthquakes recorded at local scales. In the first part of the work, we describe the procedure for extracting from the S-wave signals robust estimates of the peak displacement (PDS) and the cumulative squared velocity (IV2S). Then, exploiting a calibration data set of about 6000 earthquakes for which well-constrained M0 and theoretical ER values were available, we describe the calibration of empirical attenuation models. The coefficients and parameters obtained by calibration were then used for determining ER and M0 of a testing dataset&lt;/p&gt;

Physical significance of earthquake quanta

1996 ◽  
Vol 86 (5) ◽  
pp. 1623-1626
Author(s):  
Z. L. Wu ◽  
Y. T. Chen ◽  
S. G. Kim
Keyword(s):  
State Physics ◽  
Solid State ◽  
Stress Drop ◽  
Seismic Moment ◽  
Failure Criteria ◽  
Physical Significance ◽  
Mean Stress ◽  
Solid State Physics ◽  
The Mean ◽  
Large Earthquakes

Abstract The physical significance of “earthquake quanta” is discussed in the perspective of a proposed concept “seismon.” It is pointed out that the physical significance of earthquake quanta may be understood in the way similar to that of phonon in solid-state physics. Using the statistical properties of the seismons, the property such that for large earthquakes the mean stress drop is approximately constant, while for small events the mean stress drop increases with the seismic moment, may be obtained, without detailed considerations of the failure criteria and the interaction between different earthquake quanta.

Source retrieval for deep local earthquakes with broadband records

1993 ◽  
Vol 83 (6) ◽  
pp. 1855-1870
Author(s):  
Masayuki Kikuchi ◽  
Mizuho Ishida
Keyword(s):  
Seismic Moment ◽  
Body Wave ◽  
Time Function ◽  
P Wave ◽  
Source Time Function ◽  
Initial Portion ◽  
Large Earthquakes ◽  
Vast Range ◽  
Multiple Shock ◽  
Source Retrieval

Abstract Body wave data recorded at a small network of broadband seismograph stations are analyzed to investigate local events with focal depths deeper than about 50 km. For these events the initial portion of P-wave displacement represents well the source time function with a scaler correction for the seismic moment. The magnitudes of the analyzed earthquakes range from MW = 3.1 to 6.5. It is shown that the seismic moment M0 and the pulse width τ are well correlated as M0/τ3 = constant, indicating that the stress drop is largely constant. This dynamic similarity seems to be valid for a vast range of earthquake sizes: MW = 1 ∼ 8. It is also shown that source complexity such as a multiple shock nature is not a characteristic of only large earthquakes but is often observed even for small earthquakes.

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