Historical Seismograms Research Articles

Seismotectonic aspects of the Ms 7.3 1948 October 5 Aşgabat (Ashgabat) earthquake, Türkmenistan: right-lateral rupture across multiple fault segments, and continuing urban hazard

SUMMARY The Ms 7.3 1948 Aşgabat earthquake was one of the most devastating earthquakes of the 20th century, yet little is known about its location, style and causative fault. In this study, we bring together new seismic and geomorphic observations with previously published descriptions of surface rupture and damage distributions to determine the likely source of the earthquake. We determine the epicentre and focal mechanism of this earthquake from digitized historical seismograms and the relocation of regional seismicity to show that the earthquake most likely nucleated close to the city of Aşgabat. The earthquake ruptured a right-lateral strike-slip fault to the southeast of the city, which has a clear long-term expression in the landscape, and also likely reactivated a subparallel concealed thrust along the Gyaursdag anticline east of the city. The earthquake potentially also ruptured a right-lateral segment northwest of Aşgabat, which does not have an identifiable expression in the landscape. Using high-resolution satellite imagery and digital elevation models we investigate the geomorphology of active faulting around Aşgabat and adjacent parts of the Köpetdag (Kopeh Dagh) mountain range front, showing that there are significant strike-slip and oblique strike-slip segments adjacent to the city that apparently did not rupture in 1948, and yet show clear geomorphic expression and potential right-lateral displacement of Parthian-era (∼2000 yr) and post-Sassanian era (∼1500 yr) archaeological remains. Luminescence dating of displaced fluvial terraces west of Aşgabat yields a vertical displacement rate of 0.6 mm yr−1, though the strike-slip rate remains undetermined.

Computer Vision Algorithms of DigitSeis for Building a Vectorised Dataset of Historical Seismograms from the Archive of Royal Observatory of Belgium

Archived seismograms recorded in the 20th century present a valuable source of information for monitoring earthquake activity. However, old data, which are only available as scanned paper-based images should be digitised and converted from raster to vector format prior to reuse for geophysical modelling. Seismograms have special characteristics and specific featuresrecorded by a seismometer and encrypted in the images: signal trace lines, minute time gaps, timing and wave amplitudes. This information should be recognised and interpreted automatically when processing archives of seismograms containing large collections of data. The objective was to automatically digitise historical seismograms obtained from the archives of the Royal Observatory of Belgium (ROB). The images were originallyrecorded by the Galitzine seismometer in 1954 in Uccle seismic station, Belgium. A dataset included 145 TIFF images which required automatic approach of data processing. Software for digitising seismograms are limited and many have disadvantages. We applied the DigitSeis for machine-based vectorisation and reported here a full workflowof data processing. This included pattern recognition, classification, digitising, corrections and converting TIFFs to the digital vector format. The generated contours of signals were presented as time series and converted into digital format (mat files) which indicated information on ground motion signals contained in analog seismograms. We performed the quality control of the digitised traces in Python to evaluate the discriminating functionality of seismic signals by DigitSeis. We shown a robust approach of DigitSeis as a powerful toolset for processing analog seismic signals. The graphical visualisation of signal traces and analysis of the performed vectorisation results shown that the algorithms of data processing performed accurately and can be recommended in similar applications of seismic signal processing in future related works in geophysical research.

Computer Vision Algorithms of DigitSeis for Building a Vectorised Dataset of Historical Seismograms from the Archive of Royal Observatory of Belgium

Computer Vision Algorithms of DigitSeis for Building a Vectorised Dataset of Historical Seismograms from the Archive of Royal Observatory of Belgium

Computer Vision Algorithms of DigitSeis for Building a Vectorised Dataset of Historical Seismograms from the Archive of Royal Observatory of Belgium

Computer Vision Algorithms of DigitSeis for Building a Vectorised Dataset of Historical Seismograms from the Archive of Royal Observatory of Belgium

PAHUTE MESA TRAVEL TIMES AT KURIL–KAMCHATKA SEISMIC STATIONS

This research fulfills additional information about the lithosphere below Southeastern Asia and the northern Pacific. The area is interesting for researchers because of the Kuril–Kamchatka subducted lithosphere. The availability to study an underground structure is complicated, because of Pacific Ocean. The significance of this research concerns epicentral distances ~54°–70° or ~6000–7000 km. During the Cold War of the 20th century and the classification of information between the largest nuclear states the Soviet Union (USSR) and the United States of America (USA), data on the registration of nuclear explosions were not published, however, underground nuclear explosions (UNE) were recorded. Thanks to an employee of the laboratory 5-s of the Institute of Physics of the Earth named after O.Yu. Schmidt of the USSR Academy of Sciences Kh.D. Rubinstein is kept at the Institute for the Dynamics of Geospheres of the Russian Academy of Sciences named after Academician M.A. Sadovsky (IDG RAS). Only after 1985 reports from some seismic stations of the former USSR began to be published in the operational reports of the United Geophysical Survey of the Russian Academy of Sciences (GS RAS). As it has not been yet published anywhere, we collect them and obtain the travel times were by revising seismograms from the archives IDG RAS and GS RAS for five Kuril–Kamchatka seismic stations (Bering, Esso, Severo-Kurilsk, Kurilsk). The 48 Unites States UNE at Pahute Mesa (at Nevada Test Site) from 1968 to 1990 are used for travel time curve building. We measure P waves travel times (tp) on historical seismograms for the ray travel path between Pahute Mesa tests and Kuril–Kamchatka stations. The body-waves magnitudes (mb) vary from 5.3 to 6.5. We obtain arrivals for: 1 UNE at Bering station, 7 UNE at Esso station, 45 UNE at Petropavlovsk, 18 UNE at Severo-Kurilsk and 12 at Kurilsk. We build a travel time function using linear regression algorithm as tp=k·Δ°+b, where Δ° is the epicentral distance, k and b are arbitrary constants. We show that travel time deviations, associated with nonlinearity of the Earth. We estimate the effective velocities of P waves for the Pahute Mesa – Kuril–Kamchatka travel path as coefficient k in the linear equation. Effective velocity is equal to 7.5 km/s.

Which one of the three latest large earthquakes in Zagreb was the strongest – the 1905, 1906 or the 2020 one?

Following the damaging earthquake of 22 March 2020 (ML = 5.5, Mw = 5.3, Imax = VII EMS) in Zagreb, a question was raised whether this was the largest event after the Great Zagreb earthquake of 1880 (Imax = VIII MSK). The countercandidates are the events of 17 December 1905 and 2 January 1906, for which relevant earthquake catalogues mostly report larger or comparable magnitudes as for the earthquake of 2020, with their maximum intensities mostly within a narrow margin between VII and VII–VIII in various intensity scales. In order to resolve the question, we have (re)analysed all available macroseismic data for the two historical events, collected readings from station bulletins, and analysed available historical seismograms. Macroseismic proxy for the local magnitude (MmR) was estimated on the basis of modelled radii of isoseismals V EMS and VI EMS using the regressions derived for a set of 12 earthquakes in NW Croatia and the neighbouring areas. Macroseismic magnitude was found to be the largest for the 1906 event (MmR = 5.3), followed by MmR = 5.1 for the 2020 quake. Considering the magnitudes computed after Wiechert seismograms from the Göttingen (GTT) station, and from the amplitude/period readings reported from the German stations JEN and HOH for the earthquake of 1906, as well as the magnitudes calculated from broad-band records of the GTTG station and the stations of the Croatian network for the event of 2020, a unified local magnitude of ML = 5.3 is found for both events. The magnitudes of the 1905 earthquake were consistently the lowest of the three. Taking the uncertainties into account, the events of 1906 and 2020 should be considered approximately equal in size. However, the strongest shaking in the centre of Zagreb was caused by the 2020 event. It occurred on the reverse North Medvednica boundary fault, while the macroseismic epicentres of earthquakes of 1905 and 1906 lie practically on the trace of the nearby strike-slip Kašina fault. That Kašina fault could have been the source of the 1906 earthquake is also hinted at by the elongated region of the strongest shaking along its strike.

Magnitude of the 1920 Haiyuan Earthquake Reestimated Using Seismological and Geomorphological Methods

AbstractReported magnitudes ranging between 7.8 and 8.7 highlight a confusion about the true size of the 1920 Haiyuan earthquake, the largest earthquake recorded in the northeast Tibetan Plateau. We compiled a global data set of previously unlooked‐at historical seismograms and performed modern computational analyses on the digitized seismic records. We found the epicenter to be near Haiyuan town and obtained a moment magnitude of MW=7.9±0.2. Following traditional approaches, we obtained mB=7.9±0.3 with data from 21 stations and MS(20)=8.1±0.2 with data from three stations. Geomorphologically, we mapped the surface rupture and horizontal offsets on high‐resolution Pleiades satellite and drone imagery that covered the entire western and middle sections of the 1920 Haiyuan earthquake rupture and compiled offsets reported on the eastern section from field measurements in the 1980s. Careful discrimination between single‐event and cumulative offsets suggests average horizontal slips of 3.0±1.0 m on the western section, 4.5±1.5 m on the middle section, and 3.5±0.5 m on the eastern section, indicating a total moment magnitude of MW=7.8±0.1. Thus, the seismological and geomorphological results agree within the uncertainties, a weighted average giving a moment magnitude of MW=7.9±0.2 for the 1920 Haiyuan earthquake. It is likely that earthquake magnitudes based on the historical M were systematically overestimated.

Rescue Work and Progress of Analog Seismograms in China

Abstract Rescue work involving scanning and digitization research on historical analog seismograms nationwide in China was launched in 2017. A series of results have been accomplished. There are more than 13 million analog seismic records existing in China, and about 3 million of them were scanned by December 2019. The Second Monitoring and Application Center of China Earthquake Administration completed the phased construction of the “China Analog Seismic Record Rescue Project” in 2019, which has received a great deal of funding support. Most of the analog seismograms and geophysical records in China will be scanned in the following decade, the corresponding stations and instrument parameters will be also collected during this project to provide retrieval and download service. This article first introduces the survey statistics about scanning and digitalization progress of analog seismic records in China. Second, a management and service system for the storage and query of large scale of seismograms has been established based on distributed database and search engine. Finally, future prospects of the rescue work of analog seismograms are mentioned.

Preface to the Focus Section on Historical Seismograms

Preface to the Focus Section on Historical Seismograms

Conservation and Utilization of Historical Seismograms from Early Stage (A.D. 1904–1948), Mainland China

Abstract The history of seismographic observation in the first half of the twentieth century on the Chinese mainland can be divided into three eras. The first era was from 1904 to 1929 when there were some seismographic stations that were built in Mainland China by foreigners. The second era started from 1930 when the stations near Beijing and in Nanjing were built by the Chinese. Advanced seismographic instruments were purchased from abroad, including Wiechert instruments with the heaviest pendulum of 17,000 kg. The development of Chinese seismic observation was disrupted by the Japan invasion and war in 1937. The third era was during a time of war, from 1937 to 1948. The historical changes of seismographic stations and relevant instruments are introduced in this article. Recent effects to preserve the early historical seismograms by means of microfiches and scanning are illustrated. The contribution of these historical seismograms to the compilation of Chinese earthquake catalogs is analyzed. The deficiencies of seismogram utilization and digitalization are pointed out. Future work is proposed.

Analog Seismogram Archives at the Earthquake Research Institute, the University of Tokyo

Abstract The Earthquake Research Institute (ERI) of the University of Tokyo maintains archives of analog seismograms and mareograms. The main collection is ∼236,000 Japanese historical seismograms recorded at the University of Tokyo (at various buildings and using various instruments around Hongo [Tokyo] with a total of 189,000 records from 1881 to 1993), at the Tsukuba observatory (∼11,000 records from 1921 to 1986), and at the Wakayama seismological network (∼12,650 records from 1928 to 1968). Seismograms recorded by temporal stations at various locations in Japan for several years, typically following large earthquakes, are also included. Different types of instruments were used to record the data. The oldest record from a large earthquake is from the 1891 Nobi earthquake recorded at Hongo on a circular seismogram using an Ewing-type seismograph. Teleseismic seismograms include those from the 1899 Alaska earthquake at Hongo on an Omori-type seismograph. Imamura-type and Omori-type tremometers and strong-motion seismographs had also been used for a long time. While these seismograms were microfilmed by the 1990s, the original smoked paper records have also been archived. Foreign seismogram collections include those from earthquakes in Taiwan between 1904 and 1917 recorded in both Japan and Taiwan and those from the Canadian Seismograph Network between 1981 and 1989. For the Worldwide Standardized Seismograph Network stations, almost all (∼5,000,000) microfilm records at 167 stations from 1963 to 1988 are archived. High-resolution image scanning of analog daily seismograms at the Wakayama microearthquake network is currently being performed, and the scans are provided using Leaflet software so that the users can easily access and enlarge parts of seismograms. The tsunami waveform archive contains ∼3100 records on Japanese tide gauges from large earthquakes between 1911 and 1996. The available data, with dates and types of instruments, can be searched from the database through the website of the ERI.

Source parameters of the 1926 and 1927 Jersey earthquakes from historical, instrumental, and macroseismic data

English Channel Islands are located off Normandy coast of France within an intraplate area not associated with high seismicity rate and active tectonics. However, in July 1926 a damaging and well-documented earthquake occurred there, followed by a strongly felt event in February 1927. In this paper, we reprocess macroseismic observations, analog seismograms and bulletin data in order to re-appraise the location and magnitude of these two earthquakes. We find that the macroseismic epicentre of the 1926 Jersey earthquake is shifted to the East when compared with the location offshore South of Jersey given in both the French database SisFrance and the recent French catalog FCAT-17. Arrival-times from published data, together with our own onset-time readings, are processed in order to obtain probabilistic hypocentral locations. The maximum-likelihood instrumental epicentre of the 1926 event is located about 15 km East of Jersey Island (49.20°N, 1.82°W). This epicentre is well constrained within a 10 km radius area. The location of the 1927 epicentre is slightly south of Jersey, at a location similar to that of SisFrance, but this latter epicentre is less constrained as fewer observations are available (the Probability Density Function for the 1927 epicentre is relatively “diluted”). Focal depth remains very poorly determined for both the 1926 and 1927 events. Analysis of historical seismograms is also performed in order to determine both surface-wave and moment magnitudes, MS and MW. We find MS = 5.6 ± 0.2 for the 1926 event and MS = 5.0 for the 1927 event. Waveform fitting of some of the highest quality seismograms of the 1926 event gives us MW in the range [5.0, 5.5], depending on the chosen focal depth and focal mechanism. The 1927 Jersey earthquake is expected with an intensity magnitude MI about 0.6 smaller.

New constraints on the 1922 Atacama, Chile, earthquake from Historical seismograms

SUMMARYWe recently found the original Omori seismograms recorded at Hongo, Tokyo, of the 1922 Atacama, Chile, earthquake (MS = 8.3) in the historical seismogram archive of the Earthquake Research Institute (ERI) of the University of Tokyo. These recordings enable a quantitative investigation of long-period seismic radiation from the 1922 earthquake. We document and provide interpretation of these seismograms together with a few other seismograms from Mizusawa, Japan, Uppsala, Sweden, Strasbourg, France, Zi-ka-wei, China and De Bilt, Netherlands. The 1922 event is of significant historical interest concerning the cause of tsunami, discovery of G wave, and study of various seismic phase and first-motion data. Also, because of its spatial proximity to the 1943, 1995 and 2015 great earthquakes in Chile, the 1922 event provides useful information on similarity and variability of great earthquakes on a subduction-zone boundary. The 1922 source region, having previously ruptured in 1796 and 1819, is considered to have significant seismic hazard. The focus of this paper is to document the 1922 seismograms so that they can be used for further seismological studies on global subduction zones. Since the instrument constants of the Omori seismographs were only incompletely documented, we estimate them using the waveforms of the observed records, a calibration pulse recorded on the seismogram and the waveforms of better calibrated Uppsala Wiechert seismograms. Comparison of the Hongo Omori seismograms with those of the 1995 Antofagasta, Chile, earthquake (Mw = 8.0) and the 2015 Illapel, Chile, earthquake (Mw = 8.3) suggests that the 1922 event is similar to the 1995 and 2015 events in mechanism (i.e. on the plate boundary megathrust) and rupture characteristics (i.e. not a tsunami earthquake) with Mw = 8.6 ± 0.25. However, the initial fine scale rupture process varies significantly from event to event. The G1 and G2, and R1 and R2 of the 1922 event are comparable in amplitude, suggesting a bilateral rupture, which is uncommon for large megathrust earthquakes.

A new program on digitizing analog seismograms

Historical seismograms contain a great variety of useful information which can be used in the study of earthquakes. It is necessary for researchers to digitize analog records and extract the information just as modern computing analysis requires. Firstly, an algorithm based on color scene filed method is presented in order to digitize analog seismograms. Secondly, an interactive software program using C# has been developed to digitize seismogram traces from raster files quickly and accurately. The program can deal with gray-scale images stored in a suitable file format and it offers two different methods: manual digitization and automatic digitization. The test result of the program shows that the methods presented in this paper can lead to good performance.

Historical seismograms: Preserving an endangered species

The youth of seismology as a science, compared to the typical duration of seismic cycles, results in a relative scarcity of records of large earthquakes available for processing by modern analytical techniques, which in turn makes archived datasets of historical seismograms extremely valuable in order to enhance our understanding of the occurrence of large, destructive earthquakes. Unfortunately, the value of these datasets is not always perceived adequately by decision-making administrators, which has resulted in the destruction (or last-minute salvage) of irreplaceable datasets.We present a quick review of the nature of the datasets of seismological archives, and of specific algorithms allowing their use for the modern retrieval of the source characteristics of the relevant earthquakes. We then describe protocols for the transfer of analog datasets to digital support, including by contact-less photography when the poor physical state of the records prevents the use of mechanical scanners.Finally, we give some worldwide examples of existing collections, and of successful programs of digital archiving of these valuable datasets.

Investigation of regional seismicity before and after hydraulic fracturing in the Horn River Basin, northeast British Columbia

We systematically re-analyzed historical seismograms to verify the existence of background seismicity in the Horn River Basin of northeast British Columbia before the start of regional shale gas development. We also carefully relocated local earthquakes that occurred between December 2006 and December 2011 to delineate their spatiotemporal relationship with hydraulic fracturing (HF) operations in the region. Scattered seismic events were detected in the Horn River Basin throughout the study periods. The located seismicity within 100 km of the Fort Nelson seismic station had a clearly increasing trend, specifically in the Etsho area where most local HF operations were performed. The number of events was increased from 24 in 2002–2003 (prior to HF operations) to 131 in 2011 (peak period of HF operations). In addition, maximum magnitude of the events was shifted from ML2.9 to ML3.6 as the scale of HF operation expanded from 2006–2007 to 2011. Based on our relocated earthquake catalog, the overall b value is estimated at 1.21, which is higher than the average of tectonic/natural earthquakes of ∼1.0. Our observations highly support the likelihood of a physical relationship between HF operation and induced seismicity in the Horn River Basin. Unfortunately, due to the sparse station density in the region, depth resolution is poor for the vast majority of events in our study area. As new seismograph stations are established in northeast British Columbia, both epicentral mislocation and depth uncertainty for future events are expected to improve significantly.

On the recovery and analysis of historical seismograms

The analysis of historical seismograms has proven to be a fundamental tool to help with the definition of the seismic risk in specific regions. Indeed, modern quantitative reappraisal of relevant earthquakes that occurred before the 1960’s; i.e., prior to both the developments of modern recording instruments and the theoretical progress, has been essential for the assessment of the seismic potential of a source area. However, due to the characteristics (transducing and recording) of the old analog seismographs, the data available are affected by intrinsic uncertainties, and errors can be introduced during the processing of waveform digitization. These drawbacks can seriously influence the quality and reliability of an investigation. In general, no standard technique can be applied when dealing with historical seismograms. Thus, specific tests and cross-checks have to be designed to estimate the limits of each specific analysis. Here, we aim to provide an overview of the whole procedure while focusing on the most crucial steps, from the seismogram recovery to the application of modern techniques for the retrieval of the seismic source information. We also suggest possible checks for the robustness of the data and for the available instrument characteristics, with a description of the effects of various uncertainties on the results that can be obtained. We thus provide useful indications for the analysis of historical seismograms, and also for the correct interpretation of the resulting characteristics of the seismic source.

Station COI: Dusting Off an Old Seismic Station

Online Material: Analysis of the background seismic noise of station COI, and yearly inventory of the historical seismograms and bulletins of station COI. The seismic station COI, located in Coimbra, Portugal, is the oldest seismic station in Portugal and among the oldest in the world. Experimental seismic recording began in 1891 with an Angot seismograph (V. G. S. S. Santos, unpublished data, 1995; Custodio et al. , 2010). Continuous recording of ground motion began in 1903 with a Milne seismograph, and is still on‐going at the same site, now with a broadband Streckeisen STS‐2 seismometer. Coimbra’s observatory owns an over 100‐year long, well‐preserved collection of seismograms, seismographs and bulletins. Station COI is taken into account in early seismological works, for example, in the 1901 compilation of stations equipped with seismographs recommended by the British Association for the Advancement of Science (BAAS, 1901), in the earthquake catalog of the International Association of Seismology for the year of 1904 (Rosenthal, 1907), in the San Francisco earthquake report (Reid, 1910) or in the classical book “Seismicity of the Earth” (Gutenberg and Richter, 1954). However, throughout time station COI lost its early importance and was progressively forgotten. Station COI is missed even by recent compilations of historical seismic data (e.g., Ferrari, 2000; Schweitzer and Lee, 2003). Recently we were able to start undusting the seismological heritage of Coimbra’s station. In this paper, we present a brief history of the station. We also describe its seismographs, seismograms and bulletins, including their present state of preservation and availability. Station COI is particularly relevant for studies of earthquakes in the pre‐digital era given that: …

The 1909 Taipei earthquake-implication for seismic hazard in Taipei

The 1909 April 14 Taiwan earthquake caused significant damage in Taipei. Most of the information on this earthquake available until now is from the written reports on its macro-seismic effects and from seismic station bulletins. In view of the importance of this event for assessing the shaking hazard in the present-day Taipei, we collected historical seismograms and station bulletins of this event and investigated them in conjunction with other seismological data. We compared the observed seismograms with those from recent earthquakes in similar tectonic environments to characterize the 1909 earthquake. Despite the inevitably large uncertainties associated with old data, we conclude that the 1909 Taipei earthquake is a relatively deep (50–100 km) intraplate earthquake that occurred within the subducting Philippine Sea Plate beneath Taipei with an estimated M_W of 7 ± 0.3. Some intraplate events elsewhere in the world are enriched in high-frequency energy and the resulting ground motions can be very strong. Thus, despite its relatively large depth and a moderately large magnitude, it would be prudent to review the safety of the existing structures in Taipei against large intraplate earthquakes like the 1909 Taipei earthquake.

The south of Java earthquake of 1921 September 11: a negative search for a large interplate thrust event at the Java Trench

SUMMARY We present a detailed study of the earthquake of 1921 September 11, located between the two anomalous ‘tsunami earthquakes’ of 1994 and 2006 south of Java. Based on modern relocation techniques, a compilation of focal mechanism constraints from historical seismograms, a quantification of mantle surface waves, and a numerical simulation of its mediocre tsunami (only 10 cm at Cilacap), we conclude that the 1921 earthquake occurred at a depth of 30 km, as an intraplate earthquake in the outer rise, featuring a mostly strike-slip mechanism expressing tensional stress parallel to the direction of convergence, with a moment of 5 × 1027 dyn cm. Two other large historical earthquakes south of Java (in 1937 and 1943) are also shown to be intraplate shocks, so that the Java subduction zone lacks large interplate thrust events for the entire era of instrumental seismicity. However, this does not violate the extrapolation to large sources of the frequency-moment characteristics of modern digital data (1976–2011), thus leaving open the possibility that the Java trench might entertain occasional, if rare, mega-thrust events.