RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 8, ES1001, doi:10.2205/2005ES000195, 2006
[14] According to Hughes and Bellamy [1935] the 1930 earthquake was recorded on 13 stations at epicentral distances ranging from 0.6o to 11.2o. The fact that the earthquake was recorded up to 1200 km distance already supports a relatively large magnitude value. The reported magnitude by the International Seismological Summary (ISS) Kárnik [1969] is MS=4.6 (based on data of 2 stations) whereas in the column of remarks a magnitude M=5.0 calculated by Munuera [1963] with a local magnitude scale is given. Our assessment ( MS=4.8 ) based on macroseismic data analysis is in a very good agreement with these values. The source depth is not defined in Kárnik [1969]; it is only marked as "normal". On the other hand, the 1949 earthquake is not consigned by the ISS. Kárnk [1969] gives a magnitude (4.2) (brackets in the original) taken from Munuera [1963]. However, as it has been shown recently [López and Mu noz, 2003] the methodology used by Munuera [1963] presents some shadows really difficult to elucidate now. In an unpublished research, Sánchez-Contador [1988] calculated a local magnitude ( M L ) equation for the Mainka's seismographs and a duration magnitude ( Mt ) equation for the Vicentini seismograph of the Fabra Observatory (FBR) in Barcelona, situated approximately at one degree of distance from the epicentral zone. The application of these equations gives M L=5.0 and Mt=4.9 for the 1930 earthquake and M L=Mt=4.5 for the 1949 event. Samardjieva et al. [1998] also calculated the Mt and MS magnitudes for the Horizontal Wiechert seismograph at Toledo Observatory (TOL) and obtained 4.5 and 4.1 values, respectively, for the 1930 earthquake. The 1949 event was not recorded at that observatory.
[15] Although all presented data sustain the assumption that the 1949 earthquake had a lower magnitude than the 1930 event, in order to shed light on these discrepancies the instrumental magnitudes for both events were re-calculated using the original seismographic recordings summarized in Table 3. All the recordings have been previously scanned, digitized and processed as described in Dineva et al. [2002]. However, some problems with the stylus inscription, time marks and not damped instruments make most of the records not valid for the seismic moment calculation. The only useful records are those from Toledo Observatory. Thus, the moment magnitude ( Mw ) has been calculated for the 1930 event. The obtained ground displacement spectra ( U ) of the digitized recordings have been modelled following Brune [1970, 1971] by fitting:
![]() | (3) |
[16] Then, the seismic moment was estimated using the formulation of Keilis-Borok [1960] from the low-frequency level of the spectra of body-waves:
![]() | (4) |
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Figure 5 |
![]() | (5) |
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Figure 6 |
Citation: 2006), Macroseismic and instrumental data comprehensive analysis: Earthquake of June 2, 1930 in Catalonia (Spain), Russ. J. Earth Sci., 8, ES1001, doi:10.2205/2005ES000195.
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