Historical Catalogue Research Articles

The Curious Case of the 1919 Swaziland Earthquake

The locations of seismic events during the early twentieth century were sometimes plagued by mislocations, especially in Africa where there were few seismograph stations. In this regard, it is common to find false earthquakes erroneously listed among true ones. Without critical assessment, such events, especially in historical catalogs, have remained in subsequent earthquake catalogs including modern ones. A number of these false earthquakes have been disclosed and their nature revealed and discussed in many places around the world (e.g., Giardini and Balassanaian, 1997; Albini et al. , 2010; Grunthal and Walhstrom, 2011). The most difficult catalog records to identify and expose as false events are mislocated true earthquakes (e.g., Guidoboni and Ferrari, 1986; Bellettati et al. , 1993; Stucchi and Camassi, 1997; Glavcheva, 2004; Grunthal, 2004; Albini, 2011). These mistakes can only be identified and corrected by reviewing earthquake catalogs starting from the most recent tracing back to earlier studies for reinterpretation (Camassi, 2004; Albini, 2011). The combination of felt effects and instrumental data has helped in the relocation of some earthquakes and in some instances, in the discarding of mislocated earthquakes. The case of the 31 October 1919 Swaziland earthquake ( M s 6.5) is one example of a false earthquake found today in the catalog for Africa. The event was reported in the International Seismological Summary (ISS) bulletin with phases from 22 stations around the globe but was not reported in the popular media at the time, with no records of it having been felt even in the epicentral area. With the presence of missionaries, British agents, and many reporters in the region at that time, the lack of felt reports for this event raises the question “Did the event really occur in Swaziland or was this epicenter a mislocation?” Another event of …

The maximum earthquake in future T years: Checking by a real catalog

The studies of disaster statistics are being largely carried out in recent decades. Some recent achievements in the field can be found in Pisarenko and Rodkin (2010). An important aspect in the seismic risk assessment is the using historical earthquake catalogs and the combining historical data with instrumental ones since historical catalogs cover very long time periods and can improve seismic statistics in the higher magnitude domain considerably. We suggest the new statistical technique for this purpose and apply it to two historical Japan catalogs and the instrumental JMA catalog. The main focus of these approaches is on the occurrence of disasters of extreme sizes as the most important ones from practical point of view. Our method of statistical analysis of the size distribution in the uppermost range of extremely rare events was suggested, based on maximum size Mmax(τ) (e.g. earthquake energy, ground acceleration caused by earthquake, victims and economic losses from natural catastrophes, etc.) that will occur in a prescribed time interval τ. A new approach to the problem discrete data that we called “the magnitude spreading” is suggested. This method reduces discrete random value to continuous ones by addition a small uniformly distributed random components. We analyze this method in details and apply it to verification of parameters derived from two historical catalogs: the Usami earthquake catalog (599–1884) and the Utsu catalog (1885–1925). We compare their parameters with ones derived from the instrumental JMA catalog (1926–2014). The results of this verification are following: The Usami catalog is incompatible with the instrumental one, whereas parameters estimated from the Utsu catalog are statistically compatible in the higher magnitude domain with sample of Mmax(τ) derived from the JMA catalog.

KRISTIJONO DONELAIČIO LAIKŲ KARALIAUČIAUS BIBLIOTEKŲ VAIZDAS

At the time when Kristijonas Donelaitis visited school and went to college in Konigsberg, five public“ libraries existed in the town: the castle library (Schlossbibliothek), the university library, the city or municipal library, the library of the noble family of Wallenrodt and the library of the Secret State Chancery (Geheime Etats-Cantzley). Together, they possessed more than 25,000 volumes – the castle library with 10,000 volumes was the largest, the library of the Secret State Chancery with less than 1,000 volumes the smallest collection, while each of the remaining three libraries boasted collections of about 5,000 volumes. For a poor student who could very seldom afford the purchase of books not only these libraries were available for his reading, but – as in other cities – they also had access to private libraries, some of which even had more books than public libraries. Their owners were often professors who allowed their students to use their collections.The largest library that ever existed throughout the early modern period in Konigsberg was the one of Daniel Salthen (Salthenius, 1701–1750), who was involved as no one else in the learned education of Donelaitis: In 1731, the year of Donelaitis’ arrival he was appointed the rectorate of the cathedral school in Konigsberg, and in 1733 was given a professorship of theology at the Albertina.Large parts of the historical collections of the former Konigsberg libraries were destroyed during the Second World War. However, in the Seven Years War, when Konigsberg was occupied by the Tsar troops, complete catalogs of all “public“ libraries were made that have been preserved to our days. From Salthen’s library, as from other private libraries in Konigsberg in the mid-18th century, an auction catalog was printed. It is thus possible to reconstruct the historical collections. And despite all the destructions several thousand old prints survived the Second World War; many of them are now in the libraries of the Lithuanian Academy of Sciences and the National Library in Vilnius and can be explored there.“The Seasons” by Kristijonas Donelaitis is regarded a poetic masterpiece, the creation of which would not have been possible without a profound knowledge of ancient and contemporary European poetry. At the same time it is an innovative poem for its age, creating something new and special out of these many traditions. There seems little doubt that Donelaitis must have acquired his indisputable knowledge through reading. There is no proof whether he owned a personal library, yet its existence might certainly be presumed. Irrespective of this question the crucial period of the intellectual socialization of Donelaitis was undoubtedly the decade spent in Konigsberg. It is likely that in this decade he read many of the books whose influence can be seen in his poetry. Therefore, it is natural to think of him as a potential reader of Konigsberg libraries. The paper shows some opportunities to identify possible reading matters of Kristijonas Donelaitis on the basis of the historical catalogs of Konigsberg libraries and the still existing prints from these collections and discusses the chances to reconstruct on the basis of this material the genesis of his great poetic masterpiece more accurately than before.

KRISTIJONO DONELAIČIO LAIKŲ KARALIAUČIAUS BIBLIOTEKŲ VAIZDAS

At the time when Kristijonas Donelaitis visited school and went to college in Konigsberg, five public“ libraries existed in the town: the castle library (Schlossbibliothek), the university library, the city or municipal library, the library of the noble family of Wallenrodt and the library of the Secret State Chancery (Geheime Etats-Cantzley). Together, they possessed more than 25,000 volumes – the castle library with 10,000 volumes was the largest, the library of the Secret State Chancery with less than 1,000 volumes the smallest collection, while each of the remaining three libraries boasted collections of about 5,000 volumes. For a poor student who could very seldom afford the purchase of books not only these libraries were available for his reading, but – as in other cities – they also had access to private libraries, some of which even had more books than public libraries. Their owners were often professors who allowed their students to use their collections.The largest library that ever existed throughout the early modern period in Konigsberg was the one of Daniel Salthen (Salthenius, 1701–1750), who was involved as no one else in the learned education of Donelaitis: In 1731, the year of Donelaitis’ arrival he was appointed the rectorate of the cathedral school in Konigsberg, and in 1733 was given a professorship of theology at the Albertina.Large parts of the historical collections of the former Konigsberg libraries were destroyed during the Second World War. However, in the Seven Years War, when Konigsberg was occupied by the Tsar troops, complete catalogs of all “public“ libraries were made that have been preserved to our days. From Salthen’s library, as from other private libraries in Konigsberg in the mid-18th century, an auction catalog was printed. It is thus possible to reconstruct the historical collections. And despite all the destructions several thousand old prints survived the Second World War; many of them are now in the libraries of the Lithuanian Academy of Sciences and the National Library in Vilnius and can be explored there.“The Seasons” by Kristijonas Donelaitis is regarded a poetic masterpiece, the creation of which would not have been possible without a profound knowledge of ancient and contemporary European poetry. At the same time it is an innovative poem for its age, creating something new and special out of these many traditions. There seems little doubt that Donelaitis must have acquired his indisputable knowledge through reading. There is no proof whether he owned a personal library, yet its existence might certainly be presumed. Irrespective of this question the crucial period of the intellectual socialization of Donelaitis was undoubtedly the decade spent in Konigsberg. It is likely that in this decade he read many of the books whose influence can be seen in his poetry. Therefore, it is natural to think of him as a potential reader of Konigsberg libraries. The paper shows some opportunities to identify possible reading matters of Kristijonas Donelaitis on the basis of the historical catalogs of Konigsberg libraries and the still existing prints from these collections and discusses the chances to reconstruct on the basis of this material the genesis of his great poetic masterpiece more accurately than before.

Frank Lloyd Wright and his Manner of Thought by Jerome Klinkowitz (review)

Reviewed by: Frank Lloyd Wright and his Manner of Thought by Jerome Klinkowitz Alex Bitterman FRANK LLOYD WRIGHT AND HIS MANNER OF THOUGHT. By Jerome Klinkowitz. Madison: University of Wisconsin Press. 2014. Another book about Frank Lloyd Wright? Though seemingly unnecessary, Frank Lloyd Wright and His Manner of Thought is exactly what is needed to examine the popular architect and societal figure from a completely new perspective. Employing a completely fresh approach, author Klinkowitz delves in to the life, career, and times of Frank Lloyd Wright with delightful abandon and outstanding result. Arguably the most popular of American architects, Frank Lloyd Wright led a long and long-since celebrated career, a storied life, and has made an indelible impression on American design and culture. Many widely-available volumes survey his life and work. Klinkowitz, however, leaves the more typical assessment aside and examines Frank Lloyd Wright through the lens of his thought process. This compelling, refreshing, and absolutely fascinating approach leaves no document unturned and no story untold and would be especially of interest to architects and urban planners. This is not a volume that focuses so much on what Frank Lloyd Wright did or who he was, but instead is a meticulously researched volume that relies upon careful archival research to examine the reasons why Wright pursued a road that was neither simple nor direct. In Frank Lloyd Wright and His Manner of Thought, Klinkowitz engages his readers, calling upon them to consider what made Wright tick, as well as what made him a celebrated architect. The result is positively riveting. Too often, Frank Lloyd Wright is lampooned as a difficult or demanding figure that bullied his clients and in some ways obstructed his own success. Klinkowitz gets inside of Wright’s imaginative headspace and gently dissects the inner workings of one of the most prolific architects in American history. Klinkowitz carefully explains to the reader the reasons and rationale behind this behavior against a backdrop of twentieth-century industrialization and a zeitgeist that frames the century-long quest for a better quality of life. The book begins with a compelling introduction, “Truth against the World,” which examines the fuel for Wright’s creative spirit and unique point of view. Though Klinkowitz has chosen not to present research that encircles specific projects and periods throughout Wright’s life (as have many other biographers and chroniclers), and in doing so, the author avoids simply providing a historical catalog or chronology of the architect’s work. Instead Klinkowitz carefully weaves a compelling tapestry of historical record, introspective account, and thoughtful analysis. This book is free from unnecessarily obtuse language and is undeniably engaging, informative, and thought-provoking. Frank Lloyd Wright and His Manner of Thought is truly a pleasure to read and a significant contribution to an already crowded collection of literature that chronicles this celebrated American architect, designer, and urban planner. Truly this book will be as engaging for a broad audience of readers from architects and designers to historians and popular culturalists. Alex Bitterman Alfred State College, the State University of New York Copyright © 2015 Mid-America American Studies Association

Characterization of an Earthquake Sequence Triggered by Hydraulic Fracturing in Harrison County, Ohio

Online Material: Tables of hypoinverse earthquake locations and velocity models. To extract oil and gas in tight shale formations, hydraulic fracturing is used to stimulate fracture growth and increase permeability. Typically, low (−3.0 to 0.0 M w) magnitude earthquakes are produced during hydraulic fracturing (Maxwell et al. , 2002, 2009). In a few cases, however, hydraulic fracturing has been linked to widely observed larger, so‐called positive magnitude, earthquakes. Examples include earthquakes felt by the general population in such areas as Blackpool, England, M L 2.3 (de Pater and Baisch, 2011), Horn River Basin, Canada, M L 3.8 (British Colombia Oil and Gas Commission [BCOGC], 2012), and Oklahoma M L 2.9 (Holland, 2011, 2013) and more recently in Ohio (Skoumal et al. , 2014). In this paper, we show the first evidence of positive magnitude earthquakes on a previously unmapped fault in Harrison County, Ohio, that can be related to a hydraulic fracture operation. A series of six earthquakes were located by the Array Network Facility regional seismic network using the Incorporated Research Institutions for Seismology (IRIS) EarthScope Transportable Array (TA) stations in Ohio on 2 October 2013. These earthquakes were located south of Clendening Lake in Harrison County near the town of Uhrichsville, Ohio, and included two M w 2.0 events. This series of earthquakes was followed by four more events with M w 1.7–2.2 from 3 to 19 October. There were no felt reports for any of these earthquakes. Upon inspection of the OhioSeis seismic network catalog (Hansen and Ruff, 2003) and other available historical catalogs in the region (Stover and Coffman, 1993), this series of earthquakes …

Uncertainty in PSHA related to the parametrization of historical intensity data

Abstract. In recent times a great deal of research aimed to reduce of uncertainties in probabilistic seismic hazard analysis (PSHA). Most attention was paid to the role of ground motion prediction equations (GMPEs; see, e.g., Strasser et al., 2009), while no studies were devoted to a possible larger source of uncertainties: the historical catalogues of earthquakes. In areas where historical catalogues provide a record many centuries long and surface geology does not permit us to obtain complete catalogues of seismogenic faults at the moment, their use is unavoidable for estimating seismicity rates required for PSHA. Their use is also gaining popularity as an independent tool for the estimation of PSHA (D'Amico and Albarello, 2008) and for validation purposes (Stirling and Petersen, 2006; Mucciarelli et al., 2008). After proposing an alternative parametrization of historical macroseismic intensity, this paper is devoted to discussing what the real impact of starting uncertainties in intensities on the final uncertainties in PSHA is.

Important forgotten earthquakes for Medellin

The aim of this little paper is to disseminate between regional geoscientists an historical data about an earthquake or swarm of earthquakes, felt in what is now the city of Medellín, in 1730. As far as is known, this event has not been reported before in available historical catalogs. It is important to understand the seismic hazard of the city and the region. An brief analysis is made with the limited published historical information.

Uncertainty in recurrence rates of large magnitude events due to short historic catalogs

Seismic hazard analysis requires knowledge of the recurrence rates of large magnitude earthquakes that drive the hazard at low probabilities of interest for seismic design. Earthquake recurrence is usually determined through studies of the historic earthquake catalogue for a given region. Reliable historic catalogues generally span time periods of 100–200 years in North America, while large magnitude events (M ≥ 7) have recurrence rates on the order of hundreds or thousands of years in many areas, resulting in large uncertainty in recurrence rates for large events. Using Monte Carlo techniques and assuming typical recurrence parameters, we simulate earthquake catalogues that span long periods of time. We then split these catalogues into smaller catalogues spanning 100–200 years that mimic the length of historic catalogues. For each of these simulated “historic” catalogues, a recurrence rate for large magnitude events is determined. By comparing recurrence rates from one historic-length catalogue to another, we quantify the uncertainty associated with determining recurrence rates from short historic catalogues. The use of simulations to explore the uncertainty (rather than analytical solutions) allows us flexibility to consider issues such as the relative contributions of aleatory versus epistemic uncertainty, and the influence of fitting method, as well as lending insight into extreme-event statistics. The uncertainty in recurrence rates of large (M > 7) events is about a factor of two in regions of high seismicity, due to the shortness of historic catalogues. This uncertainty increases greatly with decreasing seismic activity. Uncertainty is dependent on the length of the catalogue as well as the fitting method used (least squares vs. maximum likelihood). Examination of 90th percentile recurrence rates reveals that epistemic uncertainty in the true parameters may cause recurrence rates determined from historic catalogues to be uncertain by a factor greater than 50.

The Largest Expected Earthquake Magnitudes in Japan: The Statistical Perspective

Abstract Earthquake catalogs are probably the most informative data source about spatiotemporal seismicity evolution. The catalog quality in one of the most active seismogenic zones in the world, Japan, is excellent, although changes in quality arising, for example, from an evolving network are clearly present. Here, we seek the best estimate for the largest expected earthquake in a given future time interval from a combination of historic and instrumental earthquake catalogs. We extend the technique introduced by Zoller et al. (2013) to estimate the maximum magnitude in a time window of length T f for earthquake catalogs with varying level of completeness. In particular, we consider the case in which two types of catalogs are available: a historic catalog and an instrumental catalog. This leads to competing interests with respect to the estimation of the two parameters from the Gutenberg–Richter law, the b ‐value and the event rate λ above a given lower‐magnitude threshold (the a ‐value). The b ‐value is estimated most precisely from the frequently occurring small earthquakes; however, the tendency of small events to cluster in aftershocks, swarms, etc. violates the assumption of a Poisson process that is used for the estimation of λ . We suggest addressing conflict by estimating b solely from instrumental seismicity and using large magnitude events from historic catalogs for the earthquake rate estimation. Applying the method to Japan, there is a probability of about 20% that the maximum expected magnitude during any future time interval of length T f =30 years is m ≥9.0. Studies of different subregions in Japan indicates high probabilities for M 8 earthquakes along the Tohoku arc and relatively low probabilities in the Tokai, Tonankai, and Nankai region. Finally, for scenarios related to long‐time horizons and high‐confidence levels, the maximum expected magnitude will be around 10.

A Synthetic Seismicity Model for the Northwestern Portion of the Xianshuihe Fault, Southwestern China: Simulation Using the Monte Carlo Method, Based on Historical Earthquake Data

Abstract In order to estimate distributions of recurrence intervals and segment interactions across the four fault segments along the northwestern portion of the Xianshuihe fault (NPXF) in southwestern China, I generate a large number of synthetic earthquake catalogs by sampling recurrence intervals and segment interactions for the four segments within the preferred ranges based on the seismogenic mechanism of fault rupture and interaction. The ranges are derived from previous studies. Those catalogs that are closest to the real historical earthquake catalog consisting of seven strong events of M ≥6.8 during 1792–1981 along the NPXF, are then selected to determine the possible distributions of the intervals and interactions. Finally, I create a synthetic earthquake catalog by using Monte Carlo sampling from the determined distributions of the intervals and interactions. The ∼40,000‐year simulated seismic activity shows good agreement with the observed data with respect to the following four statistical features. (1) Most events are single‐segment ruptures, with few rupturing two or three segments (∼8% of simulated earthquakes) and none breaking all four segments simultaneously. (2) The coefficient of variation C v of the recurrence interval tends to increase with the complexity of a segment or fault. (3) The Brownian passage time distribution represents the best fit for each of the four individual segments, whereas the Weibull distribution matches the entire NPXF best. (4) The next strong event is most likely to occur in the eastern part of the southernmost segment of the NPXF.

Comment on "Seismic Hazard Analysis for the UK: Sensitivity to Spatial Seismicity Modelling and Ground Motion Prediction Equations" by K. Goda, W. P. Aspinall, and C. A. Taylor

In the course of a recent paper on seismic‐hazard analysis issues for the United Kingdom by Goda et al. (2013), the authors apply model tests derived from Musson and Winter (2012) to the seismic source‐zone model for the United Kingdom used to inform the United Kingdom national annex to the Eurocode 8 building code (Musson and Sargeant, 2007; hereinafter: BGS2007), and also to two spatially smoothed approaches, and report better results from the latter. They do not mention that similar tests on the BGS2007 model are actually reported in BGS2007. Given that I have been advocating testing of seismic‐hazard source models for over twelve years, it would be a strange thing if the BGS2007 model had been released without such testing. BGS2007 describes how the initial model performed poorly when tested, and was modified in the course of the project to give acceptable results, an example of how testing can be used as part of an iterative process to improve model performance. The tests made by BGS2007 were made on the basis of comparing simulated earthquake catalogs derived from the model with the historical catalog. The principle (Musson, 2000, 2004) is that it should be credible that the historical catalog is a member of the set of possible catalogs derived from the model, which is something that can be checked statistically. The tests in BGS2007 were made against the number of M w 4.5 events observed in 300 years, a dataset believed to be complete. The value of M w 4.5 was used in the test in BGS2007 because this was the lower‐bound magnitude used in the hazard calculations, and therefore defined the hazard‐relevant seismicity. Goda et al. (2013) tested on events above M w 4.0 in 260 years, also a complete dataset according to BGS2007. It would be …

Reply to "Comment on 'Seismic Hazard Analysis for the U.K.: Sensitivity to Spatial Seismicity Modelling and Ground Motion Prediction Equations' by Katsuichiro Goda, Willy P. Aspinall, and Colin A. Taylor," by Roger M. W. Musson

In Goda et al. (2013), we compared three approaches to modeling spatial seismicity properties for probabilistic seismic‐hazard assessment (PSHA) in a low‐seismicity region. The objective of our paper was to introduce seismic smoothing in the context of low‐seismicity areas, such as the United Kingdom, and to investigate the implications on expected scenario events and spectral shapes from PSHA and deaggregation for such conditions. We reported some statistical test results for seismicity rates obtained from the Cornell–McGuire source‐zone method, which were based on our construal of a published outline of the British Geological Survey (BGS) model of Musson and Sargeant (2007; hereafter: MS07). The formulation of zonal activity‐rate parameters for the BGS model in our calculations apparently contains some discrepancies from those used originally by MS071, with the consequence that, for proper comparison with the MS07 findings, our statistical test results need to be revised. The main cause of discrepancies in these tests relative to MS07 is our inclusion of more simulated events in the magnitude range M 4.0–4.5 for BGS source zones EC1, EC3H, V1H, and V4, due to the way we attempted to replicate the Gutenberg–Richter parameters summarized in MS07. Also, we had to make use of an alternative published historical catalog, with slight differences from that held by BGS; other issues are related to how historical seismicity rates from such earthquake catalogs are methodologically derived. This note amends the analysis results presented in Effects of Spatial Seismicity Modelling on Seismicity Rates section in Goda et al. (2013). In particular, results shown in figures 6a and 7b,c in …

Updated seismic hazard assessment of Tunisia

Modern earthquake loss models make use of earthquake catalogs relevant to the seismic hazard assessment upon seismicity and seismotectonic analysis. The main objective of this paper is to investigate a recently compiled catalog (National Institute of Meteorology or INM catalog: 412-2011) and to generate seismic hazard maps through classical probabilistic seismic hazard assessment (PSHA) and smoothed-gridded seismicity models for Tunisia. It is now established with the local earthquake bulletin that the recent seismicity of Tunisia is sparse and moderate. Therefore, efforts must be undertaken to elaborate a robust hazard analysis for risk assessment and seismic design purposes. These recommendations follow the recently published reports by the World Bank that describe the seismic risk in Tunis City as being beyond a tolerable level with an MSK intensity level of VII. Some attempts were made during the past two decades to assess the seismic hazard for Tunisia and they have mostly failed to properly investigate the historical and instrumental seismicity catalog. This limitation also exists for the key aspect of epistemic and random uncertainties impact on the final seismic hazard assessment. This study also investigates new ground motion prediction equations suitable for use in Tunisia. The methodology applied herein uses, for the first time in PSHA of Tunisia, seismicity parameters integrated in logic tree framework to capture epistemic uncertainties through three different seismic source models. It also makes use of the recently released version of OpenQuake engine; an open-source tool for seismic hazard and risk assessment developed in the framework of the Global Earthquake Model.

The Ongoing Seismic Sequence at the Pollino Mountains, Italy

A sequence of thousands of small to moderate earthquakes has been occurring since spring 2010 in the Pollino Mountains area, southern Italy (Fig. 1), where a seismic gap was previously hypothesized by paleoseismological evidence associated with the lack of major earthquakes in historical catalogs (Michetti et al. , 2000; Cinti et al. , 2002). Seismic activity is in progress at the time of writing of this paper (December 2012) after quite a disturbing long‐term acceleration of earthquake rate and strain release (Fig. 1b). The strongest earthquake ( M L 5.0 according to the Italian Seismological Instrumental and parametric Data‐basE [ISIDE], http://iside.rm.ingv.it; last accessed September 2013) was recorded on 25 October 2012 and produced damage in the epicentral area corresponding to a maximum intensity of 6 on the European Macroseismic Scale 1998 (EMS‐98) in the localities of Mormanno, Campotenese, and Piano Incoronata (Fig. 2; D’Amico and Scarfi, 2012). Because of this earthquake, more than a thousand people were evacuated from their homes and emergency actions have been carried out by the competent institutions. This earthquake with its effects, and the increasing number and intensity of events felt by the population in the preceding months, have further encouraged the attention and efforts of civil defense operators and scientific researchers toward this peculiar seismic crisis occurring in a presumed seismic‐gap area. It should also be remarked that the Pollino area, lying at the northern edge of the Calabrian subduction zone (Fig. 1a), represents a highly deformed, very intricate sector of great geodynamic interest and still not fully understood (see, e.g., Bonini et al. , 2011; Frepoli et al. , 2011; Spina et al. , 2011; Neri et al. , 2012). The present study, which focuses on the ongoing Pollino …

Real-Time Mapping of PGA Distribution in Tehran Using TRRNet and peeqMap

Tehran megacity, the political and economical capital of Iran with population of more than eight million residents, is situated in the seismically active zone of Alborz. The seismicity pattern of this zone shows occurrence of large earthquakes in long time periods (Masson et al. , 2005). Several large earthquakes such as the 855 A.D. M s 7.1, the 958 A.D. M s 7.7, and the 1117 A.D. M s 7.2 in the historical seismic catalog of Tehran and surrounding area proves that the city has a high level of seismic risk (Fig. 1). The last disastrous example among these earthquakes was in 1830, and the city is waiting for the next large earthquake (Ambraseys and Melville, 1982; Ashtari‐Jafari, 2010). Several active faults surround Tehran including North Tehran fault, Eyvanekey fault, North and South Ray faults (Fig. 1). Apart from existence of several active faults around the city, fast growth of population and urbanization in previous decades, and lack of strong regulations for urban development increased the vulnerability of Tehran to moderate to large earthquakes (Amini‐Hosseini et al. , 2009). Figure 1. Map showing major active faults (Hessami et al. , 2003), and seismicity around Tehran. Circles, epicenters of M s>6 earthquakes; numbers, the year of earthquake occurrence. The historical earthquakes are from Ambraseys and Melville (1982). Star, the epicenter of the 17 October 2009 ( M w 4.0). NRF and SRF in the dashed square area, closely surrounding the city, refer to South Ray fault and North Ray fault, respectively. Topographic contours at 200 m intervals of the boxed area are shown in Figure 3. Mindful of the seismic risk faced by the city, the Tehran Rapid Response Network (TRRNet) has been installed in the Tehran metropolitan area …

An Earthquake Catalog for Seismic Hazard Assessment in Ecuador

Building a unified and homogeneous earthquake catalog is a preliminary step for estimating probabilistic seismic hazard in a country. Ecuador, a territory of ∼600 km×500 km, is characterized by an active seismicity, both in the shallow crust and in the subduction zone. Several international and local earthquake catalogs are available, covering different time and spatial windows, characterized by different magnitude types and uncertainties. After a careful analysis of each catalog, in particular for completeness and uncertainty levels, we propose a priority scheme for merging the instrumental catalogs. Moreover, several historical earthquakes are analyzed to estimate epicentral location and magnitude, completing the solutions obtained in a previous publication. Once the historical earthquakes are appended to the instrumental catalog, the resulting catalog covers five centuries in the Cordillera region. Next, homogenization of magnitudes and removal of aftershocks is performed; different options are studied and the impact on the recurrence curve is evaluated. For the Cordillera region within −2.5° and 1° latitude, the average occurrence of an earthquake with M w≥6.0 is 10–20 years based on the historical catalog.

The Maximum Earthquake Magnitude in a Time Horizon: Theory and Case Studies

We show how the maximum magnitude within a predefined future time horizon may be estimated from an earthquake catalog within the context of Gutenberg–Richter statistics. The aim is to carry out a rigorous uncertainty assessment, and calculate precise confidence intervals based on an imposed level of confidence α . In detail, we present a model for the estimation of the maximum magnitude to occur in a time interval T f in the future, given a complete earthquake catalog for a time period T in the past and, if available, paleoseismic events. For this goal, we solely assume that earthquakes follow a stationary Poisson process in time with unknown productivity Λ and obey the Gutenberg–Richter law in magnitude domain with unknown b ‐value. The random variables Λ and b are estimated by means of Bayes theorem with noninformative prior distributions. Results based on synthetic catalogs and on retrospective calculations of historic catalogs from the highly active area of Japan and the low‐seismicity, but high‐risk region lower Rhine embayment (LRE) in Germany indicate that the estimated magnitudes are close to the true values. Finally, we discuss whether the techniques can be extended to meet the safety requirements for critical facilities such as nuclear power plants. For this aim, the maximum magnitude for all times has to be considered. In agreement with earlier work, we find that this parameter is not a useful quantity from the viewpoint of statistical inference.

A tri-stage cluster identification model for accurate analysis of seismic catalogs

Abstract. In this paper we propose a tri-stage cluster identification model that is a combination of a simple single iteration distance algorithm and an iterative K-means algorithm. In this study of earthquake seismicity, the model considers event location, time and magnitude information from earthquake catalog data to efficiently classify events as either background or mainshock and aftershock sequences. Tests on a synthetic seismicity catalog demonstrate the efficiency of the proposed model in terms of accuracy percentage (94.81% for background and 89.46% for aftershocks). The close agreement between lambda and cumulative plots for the ideal synthetic catalog and that generated by the proposed model also supports the accuracy of the proposed technique. There is flexibility in the model design to allow for proper selection of location and magnitude ranges, depending upon the nature of the mainshocks present in the catalog. The effectiveness of the proposed model also is evaluated by the classification of events in three historic catalogs: California, Japan and Indonesia. As expected, for both synthetic and historic catalog analysis it is observed that the density of events classified as background is almost uniform throughout the region, whereas the density of aftershock events are higher near the mainshocks.

A Statistical Method for Estimating Catalog Completeness Applicable to Long-Term Nonstationary Seismicity Data

Methods for analyzing the completeness of earthquake historical catalogs are applied to estimate which part of a historical catalog likely includes all earthquakes of a certain magnitude class after a certain time in a given area. Current methods of catalog completeness estimation are not sufficient in case of long‐term nonstationary seismicity data. Such methods typically require model presumptions, whereas the method described in this study does not. We develop a statistical approach based on a deviation criterion, which is applicable to stationary, nonstationary, and even multimodal nonstationary seismicity rates. The significance of the method is tested using synthetic catalogs extracted from stationary (exponential based on a Poisson process) and nonstationary (mixed bimodal Weibull–Weibull, gamma, and log‐normal) distributions. The method is applied to different parts of the Euro‐Mediterranean region based on long‐term seismicity data.