A Regionalized Seismicity Model for Subduction Zones Based on Geodetic Strain Rates, Geomechanical Parameters, and Earthquake‐Catalog Data

2019 ◽  
Vol 109 (5) ◽  
pp. 2036-2049 ◽  
Author(s):  
José Antonio Bayona Viveros ◽  
Sebastian von Specht ◽  
Anne Strader ◽  
Sebastian Hainzl ◽  
Fabrice Cotton ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Seismic Moment ◽  
Subduction Zones ◽  
Earthquake Activity ◽  
Earthquake Catalog ◽  
Strain Rates ◽  
Earthquake Forecast ◽  
Earthquake Parameters ◽  
Seismicity Rates ◽  
Geodetic Strain

Abstract The Seismic Hazard Inferred from Tectonics based on the Global Strain Rate Map (SHIFT_GSRM) earthquake forecast was designed to provide high‐resolution estimates of global shallow seismicity to be used in seismic hazard assessment. This model combines geodetic strain rates with global earthquake parameters to characterize long‐term rates of seismic moment and earthquake activity. Although SHIFT_GSRM properly computes seismicity rates in seismically active continental regions, it underestimates earthquake rates in subduction zones by an average factor of approximately 3. We present a complementary method to SHIFT_GSRM to more accurately forecast earthquake rates in 37 subduction segments, based on the conservation of moment principle and the use of regional interface seismicity parameters, such as subduction dip angles, corner magnitudes, and coupled seismogenic thicknesses. In seven progressive steps, we find that SHIFT_GSRM earthquake‐rate underpredictions are mainly due to the utilization of a global probability function of seismic moment release that poorly captures the great variability among subduction megathrust interfaces. Retrospective test results show that the forecast is consistent with the observations during the 1 January 1977 to 31 December 2014 period. Moreover, successful pseudoprospective evaluations for the 1 January 2015 to 31 December 2018 period demonstrate the power of the regionalized earthquake model to properly estimate subduction‐zone seismicity.

Seismic moment catalog of large shallow earthquakes, 1900 to 1989

1992 ◽  
Vol 82 (3) ◽  
pp. 1306-1349 ◽  
Author(s):  
Javier F. Pacheco ◽  
Lynn R. Sykes
Keyword(s):  
Seismic Moment ◽  
Subduction Zones ◽  
B Value ◽  
Reference List ◽  
Transform Faults ◽  
Shallow Earthquakes ◽  
Seismicity Rates ◽  
Chile Earthquake ◽  
The Moment ◽  
Earthquake Process

Abstract We compile a worldwide catalog of shallow (depth < 70 km) and large (Ms ≥ 7) earthquakes recorded between 1900 and 1989. The catalog is shown to be complete and uniform at the 20-sec surface-wave magnitude Ms ≥ 7.0. We base our catalog on those of Abe (1981, 1984) and Abe and Noguchi (1983a, b) for events with Ms ≥ 7.0. Those catalogs, however, are not homogeneous in seismicity rates for the entire 90-year period. We assume that global rates of seismicity are constant on a time scale of decades and most inhomogeneities arise from changes in instrumentation and/or reporting. We correct the magnitudes to produce a homogeneous catalog. The catalog is accompanied by a reference list for all the events with seismic moment determined at periods longer than 20 sec. Using these seismic moments for great and giant earthquakes and a moment-magnitude relationship for smaller events, we produce a seismic moment catalog for large earthquakes from 1900 to 1989. The catalog is used to study the distribution of moment released worldwide. Although we assumed a constant rate of seismicity on a global basis, the rate of moment release has not been constant for the 90-year period because the latter is dominated by the few largest earthquakes. We find that the seismic moment released at subduction zones during this century constitutes 90% of all the moment released by large, shallow earthquakes on a global basis. The seismic moment released in the largest event that occurred during this century, the 1960 southern Chile earthquake, represents about 30 to 45% of the total moment released from 1900 through 1989. A frequency-size distribution of earthquakes with seismic moment yields an average slope (b value) that changes from 1.04 for magnitudes between 7.0 and 7.5 to b = 1.51 for magnitudes between 7.6 and 8.0. This change in the b value is attributed to different scaling relationships between bounded (large) and unbounded (small) earthquakes. Thus, the earthquake process does have a characteristic length scale that is set by the downdip width over which rupture in earthquakes can occur. That width is typically greater for thrust events at subduction zones than for earthquakes along transform faults and other tectonic environments.

Can Machine Learning help us in [re]assessing historical earthquakes?

2021 ◽  
Author(s):  
María del Puy Papí Isaba ◽  
Christa Hammerl ◽  
Maurizio Mattesini ◽  
Vicenta María Elisa Buforn Peiró
Keyword(s):  
Machine Learning ◽  
20Th Century ◽  
Historical Earthquakes ◽  
Earthquake Activity ◽  
Earthquake Catalog ◽  
Historical Sources ◽  
Hydro Power ◽  
Earthquake Parameters ◽  
Focal Parameters ◽  
First Time

<p>Tyrol is one of the provinces with the highest seismicity in Austria. Most of the stronger historical earthquakes occurred around Innsbruck and Hall in Tirol (1572, 1670, 1689).</p><p>Within the framework of the project[1] “Historical and recent earthquake activity in Tyrol - sources, data, seismological analysis”, a study was carried out from 2014-2020, which mainly deals with historical earthquakes in Tyrol up to 1900 but also in detail with damaging earthquakes in Tyrol in the 20th century. The project’s purpose was to create a new earthquake catalog for Tyrol, which for the first time also includes Macroseismic/Intensity Data Points (M/IDPs).</p><p>An essential aspect of this study is that the sources and literature references used for all Tyrolean earthquakes up to 1900 are largely documented. Furthermore, selected damaging earthquakes of the 20th century are reported in detail. Numerous Tyrolean archives, such as the Tyrolean Provincial Archives, and the City Archives of Hall in Tyrol, were searched for contemporary earthquake sources. Likewise, the seismic archive of the Austrian Seismological Service at ZAMG (Zentralanstalt für Meteorologie und Geodynamik) contains a wealth of valuable recent information, such as the questionnaires on earthquakes of the entire 20th century.</p><p>The very time-consuming research and documentation are followed by the conversion of the written information into earthquake parameters. Briefly outlined, this comprises the following working steps: Interpretation of the sources, assignment of geographical coordinates to the pieces of evidence, evaluation of the intensity according to the European Macroseismic Scale (EMS-98), (re)calculation of the focal parameters of all damaging earthquakes and numerous newly found earthquakes.</p><p>The latter is the content of this presentation, namely to (re-)evaluate the focal parameters for historical and recent earthquakes in Tyrol for the first time using the intensity prediction equations (IPE) with the Grid Search (GS) technique. GS has been widely used in many Machine Learning types of research when it comes to hyperparameter optimization, which in this study corresponds to the earthquake focal parameters.</p><p>We used IDPs whose intensities were mostly assessed from contemporary historical sources, such as annals, chronicles, questionnaires, newspapers, etc.</p><p>A total of 1750 M/IDPs for 35 damaging earthquakes from the Austrian Earthquake Catalogue (AEC2020) could be determined based on the historical sources. The focal parameters for these earthquakes were reevaluated by means of the IPE and GS. </p><p>Likewise, 726 new M/IDPs from a total of 154 non-damaging earthquakes not yet included in the AEC2020 were determined. For 38 of them, it was possible to calculate new sets of focal parameters.</p><p>Problems encountered, accuracy, and error of the results will be introduced in the presentation. </p><p><br><br><br></p><p> </p><div><span>[1]The project was funded by TIWAG-Tiroler Wasserkraft AG, ASFINAG Alpenstraße GmbH, Fachgruppe der Seilbahnen Tirol, Verbund Hydro Power GmbH, Amt der Tiroler Landesregierung - Abteilung Allgemeine Bauangelegenheiten, Landesgeologi, ÖBB Infrastruktur AG and ZAMG.</span></div>

scholarly journals Some preliminary results of a worldwide seismicity estimation: a case study of seismic hazard evaluation in South America

2000 ◽  
Vol 43 (1) ◽  
Author(s):  
T. M. Tsapanos ◽  
C. V. Christova
Keyword(s):  
South America ◽  
Seismic Hazard ◽  
Seismic Moment ◽  
Subduction Zones ◽  
Grid Point ◽  
Slip Rate ◽  
Hazard Evaluation ◽  
Plate Boundaries ◽  
Data Set ◽  
Seismic Moment Rate

Global data have been widely used for seismicity and seismic hazard assessment by seismologists. In the present study we evaluate worldwide seismicity in terms of maps of maximum observed magnitude (Mmax), seismic moment (M 0 ) and seismic moment rate (M 0S). The data set used consists of a complete and homogeneous global catalogue of shallow (h £ 60 km) earthquakes of magnitude MS ³ 5.5 for the time period 1894-1992. In order to construct maps of seismicity and seismic hazard the parameters a and b derived from the magnitude-frequency relationship were estimated by both: a) the least squares, and b) the maximum likelihood, methods. The values of a and b were determined considering circles centered at each grid point 1° (of a mesh 1° ´1°) and of varying radius, which starts from 30 km and moves with a step of 10 km. Only a and b values which fulfill some predefined conditions were considered in the further procedure for evaluating the seismic hazard maps. The obtained worldwide M max distribution in general delineates the contours of the plate boundaries. The highest values of M max observed are along the circum-Pacific belt and in the Himalayan area. The subduction plate boundaries are characterized by the largest amount of M 0 , while areas of continental collision are next. The highest values of seismic moment rate (per 1 year and per equal area of 10 000 km 2) are found in the Southern Himalayas. The western coasts of U.S.A., Northwestern Canada and Alaska, the Indian Ocean and the eastern rift of Africa are characterized by high values of M 0 , while most of the Pacific subduction zones have lower values of seismic moment rate. Finally we analyzed the seismic hazard in South America comparing the predicted by the NUVEL1 model convergence slip rate between Nazca and South America plates with the average slip rate due to earthquakes. This consideration allows for distinguishing between zones of high and low coupling along the studied convergence plate boundary.

A probabilistic seismic hazard model for Mainland China

2020 ◽  
Vol 36 (1_suppl) ◽  
pp. 181-209 ◽  
Author(s):  
Yufang Rong ◽  
Xiwei Xu ◽  
Jia Cheng ◽  
Guihua Chen ◽  
Harold Magistrale ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Active Faults ◽  
Mainland China ◽  
Hazard Model ◽  
Source Zone ◽  
Probabilistic Seismic Hazard ◽  
Earthquake Catalog ◽  
Geodetic Strain Rate ◽  
Geodetic Strain

We construct a probabilistic seismic hazard model for mainland China by integrating historical earthquakes, active faults, and geodetic strain rates. We delineate large seismic source zones based on geologic and seismotectonic characteristics. For each source zone, a tapered Gutenberg–Richter (TGR) distribution is used to model the total seismic activity rates. The TGR a- and b-values are calculated using a new earthquake catalog, while corner magnitudes are constrained using the seismic moment rate inferred from a geodetic strain rate model. For hazard calculations, the total TGR distribution is split into two parts, with smaller ( MW < 6.5) earthquakes being distributed within the zone using a smoothed seismicity method, and larger earthquakes put both onto active faults, based on fault slip rates and dimensions, and into the zone as background seismicity. We select ground motion models by performing residual analysis using ground motion recordings. Site amplifications are considered based on a site condition map developed using geology as a proxy. The resulting seismic hazard is consistent with the fifth-generation national seismic hazard model for most major cities.

GEAR1: A Global Earthquake Activity Rate Model Constructed from Geodetic Strain Rates and Smoothed Seismicity

2015 ◽  
Vol 105 (5) ◽  
pp. 2538-2554 ◽  
Author(s):  
P. Bird ◽  
D. D. Jackson ◽  
Y. Y. Kagan ◽  
C. Kreemer ◽  
R. S. Stein
Keyword(s):  
Earthquake Activity ◽  
Strain Rates ◽  
Rate Model ◽  
Activity Rate ◽  
Smoothed Seismicity ◽  
Geodetic Strain

scholarly journals Seismic Hazard Function Mapping Using Estimated Horizontal Crustal Strain Off West Coast Northern Sumatra

2021 ◽  
Vol 9 ◽  
Author(s):  
Wahyu Triyoso ◽  
David P. Sahara
Keyword(s):  
Seismic Hazard ◽  
Return Period ◽  
West Coast ◽  
Seismic Moment ◽  
Hazard Function ◽  
Source Area ◽  
Gps Data ◽  
Earthquake Catalog ◽  
Crustal Strain ◽  
Covariance Functions

A seismic hazard study and analysis of the megathrust source off the west coast of North Sumatra, Indonesia, were conducted based on the estimated horizontal crustal strain using the surface displacement data. This area was selected due to the availability of pre- and co-seismic Global Positioning System (GPS) data for the 2005 Nias–Simeulue Mw 8.6 event. This study aimed to estimate the seismic hazard function (SHF), which is expressed as peak ground acceleration (PGA) versus probability of exceedance (PE), for a 500 years return period using GPS data. The source area model of the Mw 8.6 event is determined based on the co-seismic GPS data. The horizontal crustal strain of the source area is estimated using least square prediction employing local covariance functions based on the horizontal displacement data. The Mw 8.6 return period is estimated by dividing the sum of the co-seismic seismic moment by the pre-seismic seismic moment based on GPS data. The seismicity rate model above a magnitude of completeness is then estimated assuming the b-value of 1 obtained on the previous study’s earthquake catalog data in the region. We show that the SHF based on the study area’s horizontal crustal strain is higher than the one based on earthquake catalogs and estimated geological sliprate data. This discrepancy is associated with the static stress increase (Coulomb failure stress, CFS) of about 0.25 bar imparted by the 2004 Aceh Mw 9.1 event that occurred in the north of the study region. We interpreted that the increase of the SHF was due to the increase in the region’s stress load, which was well documented by the GPS data.

scholarly journals Seismic and Structural Analyses of the Eastern Anatolian Region (Turkey) Using Different Probabilities of Exceedance

2021 ◽  
Vol 4 (4) ◽  
pp. 89
Author(s):  
Ercan Işık ◽  
Ehsan Harirchian ◽  
Aydın Büyüksaraç ◽  
Yunus Levent Ekinci
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Seismic Design ◽  
Seismic Moment ◽  
Peak Ground Acceleration ◽  
Earthquake Ground Motion ◽  
Earthquake Risk ◽  
Ground Acceleration ◽  
Earthquake Parameters ◽  
Seismic Design Code

Seismic hazard analysis of the earthquake-prone Eastern Anatolian Region (Turkey) has become more important due to its growing strategic importance as a global energy corridor. Most of the cities in that region have experienced the loss of life and property due to significant earthquakes. Thus, in this study, we attempted to estimate the seismic hazard in that region. Seismic moment variations were obtained using different types of earthquake magnitudes such as Mw, Ms, and Mb. The earthquake parameters were also determined for all provincial centers using the earthquake ground motion levels with some probabilities of exceedance. The spectral acceleration coefficients were compared based on the current and previous seismic design codes of the country. Additionally, structural analyses were performed using different earthquake ground motion levels for the Bingöl province, which has the highest peak ground acceleration values for a sample reinforced concrete building. The highest seismic moment variations were found between the Van and Hakkari provinces. The findings also showed that the peak ground acceleration values varied between 0.2–0.7 g for earthquakes, with a repetition period of 475 years. A comparison of the probabilistic seismic hazard curves of the Bingöl province with the well-known attenuation relationships showed that the current seismic design code indicates a higher earthquake risk than most of the others.

Glacial Isostatic Adjustment as a process of deformation but not seismicity in Western Alps: Coupling geodetical strain rate and numerical modeling 

2021 ◽  
Author(s):  
Juliette Grosset ◽  
Stéphane Mazzotti ◽  
Philippe Vernant
Keyword(s):  
Numerical Modeling ◽  
Seismic Hazard ◽  
Strain Rate ◽  
Western Alps ◽  
Glacial Isostatic Adjustment ◽  
Strain Rates ◽  
Fault Activity ◽  
Isostatic Adjustment ◽  
Geodetic Strain Rate ◽  
Geodetic Strain

&lt;p&gt;In the last decade, geodetic data has become fundamental in studies of active faults, seismicity and seismic hazard. In particular, GNSS strain rates and velocities are used to constrain fault-slip rates and seismicity parameters, on the premise that these short-term (ca. 10 yr) measurements are representative of long-term (10&lt;sup&gt;4&lt;/sup&gt;&amp;#8211;10&lt;sup&gt;6&lt;/sup&gt; yr) fault activity. The Western Alps are a good example of such development in a very-low-strain region with a high-density ongoing seismic activity. There, the first-order agreement between GNSS strain rates and earthquake deformation patterns suggest that a large part of the geodetic deformation observed in the area is seismic. This correlation also suggests that geodetic strain rates can provide constraints on seismicity and seismic hazard. With a numerical modeling approach, we point out the similarities between strain rates predicted for Glacial Isostatic Adjustment (GIA) from the Last Glacial Maximum and the geodetic strain rate field, suggesting that a large part of the GNSS signal is related to GIA. However, we show that the apparent compatibility between geodetic strain rates and seismicity hides a strain rate - stress paradox. In fact, stress perturbations due to GIA are not compatible with observed seismicity, and even tend to inhibit fault activity (as observed from focal mechanisms). Thus, the Western Alps present a typical example of a tectonic system where a transient deformation process precludes, or at least strongly complexifies, the use of geodetic strain rates in seismicity and seismic hazard analyses.&lt;/p&gt;

scholarly journals A New Smoothed Seismicity Approach to Include Aftershocks and Foreshocks in Spatial Earthquake Forecasting: Application to the Global Mw ≥ 5.5 Seismicity

2021 ◽  
Vol 11 (22) ◽  
pp. 10899
Author(s):  
Matteo Taroni ◽  
Aybige Akinci
Keyword(s):  
Seismic Hazard ◽  
Smoothing Method ◽  
Earthquake Forecasting ◽  
Earthquake Catalog ◽  
Significant Information ◽  
Adaptive Smoothing ◽  
Time Space ◽  
Seismicity Models ◽  
Seismicity Rates ◽  
Smoothed Seismicity

Seismicity-based earthquake forecasting models have been primarily studied and developed over the past twenty years. These models mainly rely on seismicity catalogs as their data source and provide forecasts in time, space, and magnitude in a quantifiable manner. In this study, we presented a technique to better determine future earthquakes in space based on spatially smoothed seismicity. The improvement’s main objective is to use foreshock and aftershock events together with their mainshocks. Time-independent earthquake forecast models are often developed using declustered catalogs, where smaller-magnitude events regarding their mainshocks are removed from the catalog. Declustered catalogs are required in the probabilistic seismic hazard analysis (PSHA) to hold the Poisson assumption that the events are independent in time and space. However, as highlighted and presented by many recent studies, removing such events from seismic catalogs may lead to underestimating seismicity rates and, consequently, the final seismic hazard in terms of ground shaking. Our study also demonstrated that considering the complete catalog may improve future earthquakes’ spatial forecast. To do so, we adopted two different smoothed seismicity methods: (1) the fixed smoothing method, which uses spatially uniform smoothing parameters, and (2) the adaptive smoothing method, which relates an individual smoothing distance for each earthquake. The smoothed seismicity models are constructed by using the global earthquake catalog with Mw ≥ 5.5 events. We reported progress on comparing smoothed seismicity models developed by calculating and evaluating the joint log-likelihoods. Our resulting forecast shows a significant information gain concerning both fixed and adaptive smoothing model forecasts. Our findings indicate that complete catalogs are a notable feature for increasing the spatial variation skill of seismicity forecasts.

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