Historical seismograms for unravelling a mysterious earthquake: The 1907 Sumatra Earthquake

Abstract

S U M M A R YHistory of instrumental seismology is short. Seismograms are available only for a little more than 100 years; high-quality seismograms are available only for the last 50 years and the seismological database is very limited in time. To extend the database, seismograms of old events are of vital importance. Many unusual earthquakes are known to have occurred, but their seismological characteristics are poorly known. The 1907 Sumatra earthquake is one of them (1907 January 4, M = 7.6). Gutenberg and Richter located this event in the outer-rise area of the Sunda arc. This earthquake is known to be anomalous because of its extensive tsunami, which is disproportionate of its magnitude. The tsunami affected the coastal areas over 950 km along the Sumatran coast. We investigated this earthquake using the historical seismograms we could collect from several seismological observatories. We examined the P-wave arrival times listed in the Strassburg Bulletin (1912) and other station bulletins. The scatter of the Observed−Computed traveltime residuals ranges from -30 to 30 s, too large to locate the event accurately. The uncertainty of the epicentre estimated from an S-P grid-search relocation study is at least 1 • (∼110 km). We interpreted the Omori seismograms from Osaka, Mizusawa and Tokyo, and the Wiechert seismograms from Göttingen and Uppsala by comparing them with the seismograms simulated from modern broad-band seismograms of the 2002, 2008 and two 2010 Sumatra earthquakes which occurred near the 1907 earthquake. From the amplitude of Rayleigh waves recorded on the Omori seismograms we conclude that the magnitude of the 1907 earthquake at about 30 to 40 s is about 7.8 (i.e. 7.5 to 8.0). The SH waveforms recorded on the Göttingen and Uppsala seismograms suggest that the 1907 earthquake is a thrust earthquake at a shallow depth around 30 km. The most likely scenario is that the 1907 earthquake initiated on the subduction interface, and slowly ruptured up-dip into the shallow sediments and caused the extensive tsunami. Although their quantity and quality are limited, historical seismograms provide key quantitative information about old events that cannot be obtained otherwise. This underscores the importance of preserving historical seismograms.

Possible large near-trench slip during the 2011 M w 9.0 off the Pacific coast of Tohoku Earthquake

“…However, the problem is important; establishing whether or not the up-dip region has failed in a great earthquake is central to assessing the potential for future earthquakes that can be particularly tsunamigenic. The 1907 Sumatra (Kanamori et al, 2010) and 2010 Mentawai (M w 7.8) (Lay et al, 2011a) tsunami earthquakes ruptured narrow margins up-dip of deeper great underthrusting ruptures, and produced larger tsunami run-ups than did the larger, but deeper events adjacent to them. The occurrence of tsunami earthquakes, which characteristically have long source process times and weak short-period radiation (e.g., Kanamori, 1972;Kanamori and Kikuchi, 1993;Polet and Kanamori, 2000;Bilek and Lay, 2002; al., 2006) must involve rather large ocean bottom deformations indicative of large slips on the megathrust or on splay faults (Fukao, 1979;Pelayo and Wiens, 1992).…”

Seismic parameters re-determined from historical seismograms of 1935-Erdek–Marmara Island and 1963-Çınarcık Earthquakes

“…We also used the IASPEI91 velocity model (Kennett and Engdahl 1991) to check the reliability longitude and 10 km in latitude. Although errors in longitude and latitude seem to be large for these events, it is possible to observe the large confidence limits for the historical earthquakes, also in the published papers such as Kanamori et al (2010), Batlló et al (2008Batlló et al ( , 2010 and Tobin and Sykes (1968). The data obtained from the ISS Bulletin for this earthquake indicated large errors during the process of epicentral location.…”

“…Vectorization process is of considerable effort due to many problems that arise from quality of trace on the paper and the mechanism of traditional seismometers. Examples are pen slipping on the paper and little oscillations that are interpreted as noise on the trace because of instrumentation (Batlló et al 2008;Kanamori et al 2010). Correct identification of the earthquake to be studied can also be troublesome, which necessitates counting very carefully time marks available on records.…”

“…Usually the information necessary for all the process of the analyzing of these records, such as instrument constants and time accuracy, is missing or doubtful (Batlló et al 2008;Kanamori 1988;Abe 1994). The importance of studying historical earthquakes by analyzing original records through the modern techniques has been realized by many researchers over the world (e.g., Baskoutas et al 2000;Dineva et al 2002;Kanamori et al 2010;Lee et al 1988;Pino et al 2000Pino et al , 2008Schlupp 1996;Schlupp and Cisternas 2007;Stich et al 2003Stich et al , 2005Teves-Costa et al 1999;Cadek 1987;Abe 1994;Rivera et al 2002;Kikuchi et al 2003), which presented different methods and stimulated to carry out more comprehensive investigations about historical earthquakes over the world.…”

Converting scanned images of seismic reflection data into SEG-Y format

“…Within the field of seismology digital recording became standard in the 1970s and therefore, the majority of data collected earlier were stored only on paper or film. Kanamori et al (2010) and An et al (2015) provide examples of how re-analysis of historical data can provide insight into previous seismic events and improve the understanding of the Earth's structure. A range of initiatives have been set up to digitize and rescue seismological archives from around the world (Okal 2015).…”