scholarly journals KASTORIA “BLIND” ACTIVE FAULT: HAZARDOUS SEISMOGENIC FAULT OF THE NW GREECE

2017 ◽  
Vol 43 (1) ◽  
pp. 442
Author(s):  
Ch. P. Metaxas ◽  
N.S. Lalechos ◽  
S.N. Lalechos
Keyword(s):  
Hazard Analysis ◽  
Slip Rate ◽  
Recurrence Time ◽  
Seismic Cycle ◽  
Seismogenic Fault ◽  
Ground Shaking ◽  
Seismicity Parameters ◽  
River Bed ◽  
Seismicity Rates ◽  
Eastern Edge

The Aliakmon river bed, as well as a series of certain parallel narrow grabens, striking NW-SE are filled with Neogene-Quaternary deposits; thus showing the existence of the covered, “blind”, fault zone, which borders the Eastern edge of Meso-Hellenic Trench and passes in close vicinity to the Kastoria town. Distribution of earthquakes epicentres (M≥4.0, for the period of 1930-2009) along this segmented rupture zone, proves the existence at depth of an active seismogenic fault which has generated some strong earthquakes in the past: 1709, M = 6.0; 1812, M = 6.5 and 1894, M = 6.1 (~ 100-year Recurrence Time events). The calculations of Lapsed Rate characterizing the stage of the fault seismic cycle (LR = 115%) show that the active Kastoria fault could be in a pre-seismic stage of its seismic cycle. Applying the seismicity rates model (time-independent Gutenberg-Richter recurrence model) and using the fault seismicity parameters, obtained inside the fault influence zone, as input in EZ-FRISK® software, the Probabilistic Seismic Hazard Analysis has been carried out for the area of Kastoria town. The results show that calculated magnitude for event with 100- year recurrence time is ~6.1, which correspond to the magnitude of three events, occurred at the fault during the last 300 years (corresponding average slip rate . 3 mm/year). As the calculated Hazard Curve shows, the event of that range could give ground shaking in the Kastoria town in the order of 0.625 g at the spectral period of 0.3 sec.

A proposed source model for the great Kau, Hawaii, earthquake of 1868

1988 ◽  
Vol 78 (4) ◽  
pp. 1450-1462
Author(s):  
Max Wyss
Keyword(s):  
The United States ◽  
Source Model ◽  
Recurrence Time ◽  
Sediment Layer ◽  
Ground Shaking ◽  
Mauna Loa ◽  
Rupture Plane ◽  
Felt Area ◽  
Eastern Edge ◽  
Oceanic Sediment

Abstract On 2 April 1868, an earthquake occurred which destroyed all stone buildings in southern Hawaii. It was felt on Kauai Island at 600 km, and ground shaking of intensity VII was reported up to 130 km distance. Based on the magnitude versus felt-area relationship for Hawaii, it is estimated that the magnitude of the earthquake was about 8. The foreshock sequence lasted 5 days, and the aftershocks lasted for years to perhaps a decade. It appears that this earthquake was one of the very few largest events in historic time in the United States, excluding Alaska, but its return period is unknown. It is proposed that the source of this earthquake was slip of the upper crust towards the southeast along a near-horizontal plane at approximately 9 km depth. The rupture plane may have had dimensions of at least 50 km × 80 km. It is proposed that its eastern edge extended from near Mauna Loa's summit to the south along the volcano's southwest rift. In this model, magma intrusions into Mauna Loa and its southwest rift provide the stresses which act perpendicular to the rift and which push the volcano's southwest flank away from the edifice of the island of Hawaii. The oceanic sediment layer upon which this edifice is deposited acts as a layer of weakness containing the fault plane. This model explains the eruptive pattern of Mauna Loa and its southwest rift, as well as the growing separation between the southwest rift zones of the two volcanoes: Kilauea and Mauna Loa. Geodetic monitoring of southern Hawaii, particularly of the area between the two active volcano's southwest rifts, could test this hypothesis and lead to an estimate of the recurrence time.

The probability of large earthquakes cannot be calculated from seismicity rates

2020 ◽  
Author(s):  
Max Wyss
Keyword(s):  
Seismic Waves ◽  
Slip Rate ◽  
Strike Slip ◽  
Magnitude Scale ◽  
Recurrence Time ◽  
Normal Faults ◽  
Earthquake Probability ◽  
San Andreas ◽  
Seismicity Rates ◽  
Large Earthquakes

<p>The hypothesis that extrapolation of the Gutenberg-Richter (GR) relationship allows estimates of the probability of large earthquakes is incorrect. For nearly 200 faults for which the recurrence time, T<sub>r</sub> (1/probability of occurrence), is known from trenching and geodetically measured deformation rates, it has been shown that T<sub>r</sub> based on seismicity is overestimated typically by one order of magnitude or more. The reason for this is that there are not enough earthquakes along major faults. In some cases there are too few earthquakes for the fault to be mapped based on seismicity. Some examples are the following rupture segments of great faults: the 1717 Alpine Fault, the 1856 San Andreas, the 1906 San Andreas, the 2001 Denali earthquakes, for which geological Tr are 100 years to 300 years and seismicity T<sub>r</sub> are 10,000 to 100,000 years. In addition, the hypothesis leads to impossible results when one considers the dependence of the b-value on stress. It has been shown that thrusts, strike-slip and normal faults have low, intermediate and high b-values, respectively. This implies that, regardless of local slip rates, the probability of large earthquakes predicted by the hypothesis is high, intermediate and low in thrust, strike-slip, and normal faulting, respectively. Measurements of recurrence probability show a different dependence: earthquake probability depends on slip rate. Finally, the hypothesis predicts different probabilities for large earthquakes, depending on the magnitude scale used. For the 1906 rupture segment, the difference in probability of an M8 earthquake is approximately a factor of 50, using the two available catalogs. Various countries measure earthquake magnitude on their own scale that is intended to agree with the M<sub>L</sub> scale of California or the M<sub>S</sub> scale of the USGS. However, it is not trivial to match a scale that is valid for a different region with different attenuation of seismic waves. As a result, some regional M-scales differ from the global M<sub>S</sub> scale, which yields different T<sub>r</sub> for the same Mmax in the same region, depending on whether the global or local magnitude scale is used. Based on the aforementioned facts, the hypothesis that probabilities of large earthquakes can be estimated by extrapolating the GR relationship has to be abandoned.</p>

Complex Slip Distribution of the 2021 Mw 7.4 Maduo, China, Earthquake: An Event Occurring on the Slowly Slipping Fault

2021 ◽  
Author(s):  
Rumeng Guo ◽  
Hongfeng Yang ◽  
Yu Li ◽  
Yong Zheng ◽  
Lupeng Zhang
Keyword(s):  
Slip Rate ◽  
Slip Distribution ◽  
Seismic Gap ◽  
Seismogenic Fault ◽  
Coseismic Slip ◽  
Slip Rates ◽  
Kunlun Mountain ◽  
Coulomb Failure ◽  
Main Fault ◽  
Large Earthquakes

Abstract The 21 May 2021 Maduo earthquake occurred on the Kunlun Mountain Pass–Jiangcuo fault (KMPJF), a seismogenic fault with no documented large earthquakes. To probe its kinematics, we first estimate the slip rates of the KMPJF and Tuosuo Lake segment (TLS, ∼75 km north of the KMPJF) of the East Kunlun fault (EKLF) based on the secular Global Positioning System (GPS) data using the Markov chain Monte Carlo method. Our model reveals that the slip rates of the KMPJF and TLS are 1.7 ± 0.8 and 7.1 ± 0.3 mm/yr, respectively. Then, we invert high-resolution GPS and Interferometric Synthetic Aperture Radar observations to decipher the fault geometry and detailed coseismic slip distribution associated with the Maduo earthquake. The geometry of the KMPFJ significantly varies along strike, composed of five fault subsegments. The most slip is accommodated by two steeply dipping fault segments, with the patch of large sinistral slip concentrated in the shallow depth on a simple straight structure. The released seismic moment is ∼1.5×1020  N·m, equivalent to an Mw 7.39 event, with a peak slip of ∼9.3 m. Combining the average coseismic slip and slip rate of the main fault, an earthquake recurrence period of ∼1250−400+1120  yr is estimated. The Maduo earthquake reminds us to reevaluate the potential of seismic gaps where slip rates are low. Based on our calculated Coulomb failure stress, the Maduo earthquake imposes positive stress on the Maqin–Maqu segment of the EKLF, a long-recognized seismic gap, implying that it may accelerate the occurrence of the next major event in this region.

The Gutenberg-Richter or characteristic earthquake distribution, which is it?

1994 ◽  
Vol 84 (6) ◽  
pp. 1940-1959 ◽  
Author(s):  
Steven G. Wesnousky
Keyword(s):  
Seismic Hazard ◽  
Hazard Analysis ◽  
Slip Rate ◽  
Historical Earthquakes ◽  
Practical Implementation ◽  
Characteristic Earthquake ◽  
Earthquake Model ◽  
Earthquake Distribution ◽  
Fault Trace ◽  
Major Strike

Abstract Paleoearthquake and fault slip-rate data are combined with the CIT-USGS catalog for the period 1944 to 1992 to examine the shape of the magnitude-frequency distribution along the major strike-slip faults of southern California. The resulting distributions for the Newport-Inglewood, Elsinore, Garlock, and San Andreas faults are in accord with the characteristic earthquake model of fault behavior. The distribution observed along the San Jacinto fault satisfies the Gutenberg-Richter relationship. If attention is limited to segments of the San Jacinto that are marked by the rupture zones of large historical earthquakes or distinct steps in fault trace, the observed distribution along each segment is consistent with the characteristic earthquake model. The Gutenberg-Richter distribution observed for the entirety of the San Jacinto may reflect the sum of seismicity along a number of distinct fault segments, each of which displays a characteristic earthquake distribution. The limited period of instrumental recording is insufficient to disprove the hypothesis that all faults will display a Gutenberg-Richter distribution when averaged over the course of a complete earthquake cycle. But, given that (1) the last 5 decades of seismicity are the best indicators of the expected level of small to moderate-size earthquakes in the next 50 years, and (2) it is generally about this period of time that is of interest in seismic hazard and engineering analysis, the answer to the question posed in the title of the article, at least when concerned with practical implementation of seismic hazard analysis at sites along these major faults, appears to be the “characteristic earthquake distribution.”

Effects of temporal variations in seismicity on seismic hazard

1981 ◽  
Vol 71 (1) ◽  
pp. 321-334
Author(s):  
Robin K. McGuire ◽  
Theodore P. Barnhard
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
Seismic Activity ◽  
Time Window ◽  
Hazard Analysis ◽  
The United States ◽  
Temporal Variations ◽  
Seismogenic Zone ◽  
Eastern United States ◽  
Ground Shaking

abstract The accuracy of stationary mathematical models of seismicity for calculating probabilities of damaging shaking is examined using the history of earthquakes in China from 1350 A.D. to 1949 A.D. During this time, rates of seismic activity varied periodically by a factor of 10. Probabilities of damaging shaking are calculated in 62 cities in North China using 50 yr of earthquake data to estimate seismicity parameters; the probabilities are compared to statistics of damaging shaking in the same cities for 50 yr following the data window. These comparisons indicate that the seismic hazard analysis is accurate if: (1) the maximum possible earthquake size in each seismogenic zone is determined from the entire seismic history rather than from a short-time window; and (2) the future seismic activity can be estimated accurately. The first condition emphasizes the importance of realistically estimating the maximum possible size of earthquakes on faults. The second indicates the need to understand possible trends in seismic activity where these exist, or to develop an earthquake prediction capability with which to estimate future activity. Without the capability of estimating future seismicity, stationary models provide less accurate but generally conservative indications of seismic ground-shaking hazard. In the United States, the available earthquake history is brief but gives no indication of changing rates of activity. The rate of seismic strain release in the Central and Eastern United States has been constant over the last 180 yr, and the geological record of earthquakes on the southern San Andreas Fault indicates no temporal trend for large shocks over the last 15 centuries. Both observations imply that seismic activity is either stationary or of such a long period that it may be treated as stationary for seismic hazard analyses in the United States.

scholarly journals Probabilistic seismic hazard analysis using the logic tree approach – Patna district (India)

2019 ◽  
Vol 19 (10) ◽  
pp. 2097-2115 ◽  
Author(s):  
Panjamani Anbazhagan ◽  
Ketan Bajaj ◽  
Karanpreet Matharu ◽  
Sayed S. R. Moustafa ◽  
Nassir S. N. Al-Arifi
Keyword(s):  
Epistemic Uncertainty ◽  
Hazard Analysis ◽  
Response Spectra ◽  
Maximum Magnitude ◽  
Logic Tree ◽  
Ground Acceleration ◽  
Incremental Method ◽  
Seismicity Parameters ◽  
Hazard Response ◽  
Tree Approach

Abstract. Peak ground acceleration (PGA) and study area (SA) distribution for the Patna district are presented considering both the classical and zoneless approaches through a logic tree framework to capture the epistemic uncertainty. Seismicity parameters are calculated by considering completed and mixed earthquake data. Maximum magnitude is calculated using three methods, namely the incremental method, Kijko method, and regional rupture characteristics approach. The best suitable ground motion prediction equations (GMPEs) are selected by carrying out an “efficacy test” using log likelihood. Uniform hazard response spectra have been compared with Indian standard BIS 1893. PGA varies from 0.38 to 0.30 g from the southern to northern periphery considering 2 % probability of exceedance in 50 years.

scholarly journals The cryptic seismic potential of blind faults revealed by off-fault geomorphology, Pichilemu, Chile.

2020 ◽  
Author(s):  
Julius Jara-Muñoz ◽  
Daniel Melnick ◽  
Anne Socquet ◽  
Joaquin Cortés-Aranda ◽  
Dominik Brill ◽  
...  
Keyword(s):  
Slip Rate ◽  
Active Regions ◽  
Seismic Hazards ◽  
Recurrence Time ◽  
Diagnostic Features ◽  
Seismic Potential ◽  
Megathrust Earthquakes ◽  
Marine Terraces ◽  
Stress Changes ◽  
Geomorphic Features

Abstract In seismically-active regions, mapping capable faults and estimating their recurrence time is the first step to assess seismic hazards. Fault maps are commonly based on geologic and geomorphic features evident at the surface; however, mapping blind faults and estimating their seismic potential is challenging because on-fault diagnostic features are absent. Here, we study the Pichilemu Fault in coastal Chile, unknown until it generated a M7.0 earthquake in 2010. The lack of evident surface faulting suggests a partly-hidden blind fault. Using off-fault deformed marine terraces, we estimate a slip-rate of 0.42 ± 0.04 m/ka, which when integrated with deformation estimated from satellite geodesy during the 2010 earthquake suggests a 2.5 ± 0.25 ka recurrence time for M6.6-6.9 extensional earthquakes. We propose that extension is associated with stress changes during megathrust earthquakes and accommodated by sporadic slip during upper-plate earthquakes. Our results have implications for assessing the seismic potential of cryptic faults along seismically-active coasts.

scholarly journals A declustered earthquake catalog for the Iranian Plateau

2015 ◽  
Vol 57 (6) ◽  
Author(s):  
Seyed Hasan Mousavi-Bafrouei ◽  
Noorbakhsh Mirzaei ◽  
Elham Shabani
Keyword(s):  
Seismic Hazard ◽  
Hazard Analysis ◽  
Time Windows ◽  
Recurrence Time ◽  
Earthquake Catalog ◽  
Magnitude Of Completeness ◽  
Iranian Plateau ◽  
Seismic Stations ◽  
International Agencies ◽  
Seismotectonic Province

A unified catalog of earthquakes in Iran and adjacent regions (the area bounded in 22<sup>º</sup>-42<sup>º</sup>N and 42<sup>º</sup>-66<sup>º</sup>E) covering the period of 4<sup>th</sup> century B.C. through 2012 with M<sub>w</sub>≥4 is provided. The catalog includes all events for which magnitude have been determined by international agencies and most reliable individual sources. Since the recurrence time of maximum credible earthquake cannot be directly estimated from the m<sub>b</sub>, empirical formulae are established to convert m<sub>b</sub> to M<sub>s</sub>, m<sub>b</sub> to M<sub>w</sub> and M<sub>s</sub> to M<sub>w</sub> for each major seismotectonic province separately. The unified catalog is declustered using conjugated distance-time windows. In order to estimate completeness thresholds, magnitude-time (M-T) diagram and Stepp’s method are applied on the declustered catalog for each seismotectonic province. The magnitude of completeness (M<sub>c</sub>) decreases with development of local and regional seismic stations. The results of present study are particularly important in seismic hazard analysis in Iran.

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.

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