A magnitude scale for very large earthquakes

Purcaru, G.; Berckhemer, H.

doi:10.1016/0040-1951(78)90177-4

Cited by 127 publications

(36 citation statements)

References 5 publications

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“…From the limited number of earthquakes listed, an effort was made to find independently published estimates of scalar moments. For this, compilations by KANAMORI and ANDERSON (1975), KANA-MORI (1977), PURCARU and BERCKHEMER (1978), and OHNAKA (1978) were most useful. Table 2 lists 34 moment-energy paris describing 20 earthquakes.…”

Section: Relationships Of Tsunami Generation and The Earthquake Sourcementioning

confidence: 99%

Relationships of tsunami generation and an earthquake source.

Ward

1980

J,Phys,Earth

155

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This paper presents a theory of tsunami generation and propagation on a spherically symmetric, self-gravitating, elastic Earth in terms of normal modes. We predict the character of newborn tsunamis at regional far field distances from a simply parameterized moment tensor point source with step function time history. Tsunami eigenfunctions are shown to penetrate the Earth from tens of kilometers at 2,000 second period to tens of meters at 20 second period. This behavior explains why the longest tsunami periods are the only ones influenced by crust and mantle structure and why they are preferentially excited by submarine earthquakes.We find that large tsunamis need sizable parent earthquakes because over 96% of their energy is concentrated in the ocean. This makes the entire solid Earth virtually a node for tsunami generation. The excitation of tsunami modes is strongly dependent upon the moment, mechanism and depth of faulting. Calculated tsunami energy, ET, can vary by a factor of 100 for sources of equal moment within 30 kilometers of the sea floor. model predicts that ET is proportional to MM20. The ratio of tsunami to radiated seismic energy is less than 1% for all but the largest events. We believe that this theory coupled with a seismic source recovery technique could be a realistic basis for the forecasting of potentially dangerous tsunamis in real time.

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Section: Relationships Of Tsunami Generation and The Earthquake Sourcementioning

confidence: 99%

Relationships of tsunami generation and an earthquake source.

Ward

1980

J,Phys,Earth

155

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show abstract

“…Similarly the regional value of c for northeast India, Greece, Aegean area, the western coast of South and Central America and for Nepal Himalaya is estimated to be as 0.36, 0.32, 0.35, 0.21 and 0.32, respectively. The seismic moment, M o (moment released), for an individual earthquake in the sequence is planned from the surface wave magnitude using the following relationship (Purcaru and Berckhemer, 1978):…”

Section: Methodology Applied and Calculationmentioning

confidence: 99%

Time-predictable model applicability for earthquake occurrence in northeast India and vicinity

Panthi

Shanker

Singh

et al. 2011

Nat. Hazards Earth Syst. Sci.

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Abstract. Northeast India and its vicinity is one of the seismically most active regions in the world, where a few large and several moderate earthquakes have occurred in the past. In this study the region of northeast India has been considered for an earthquake generation model using earthquake data as reported by earthquake catalogues National Geophysical Data Centre, National Earthquake Information Centre, United States Geological Survey and from book prepared by Gupta et al. (1986) for the period 1906-2008. The events having a surface wave magnitude of M s ≥ 5.5 were considered for statistical analysis. In this region, nineteen seismogenic sources were identified by the observation of clustering of earthquakes. It is observed that the time interval between the two consecutive mainshocks depends upon the preceding mainshock magnitude (M p ) and not on the following mainshock (M f ). This result corroborates the validity of time-predictable model in northeast India and its adjoining regions. A linear relation between the logarithm of repeat time (T ) of two consecutive events and the magnitude of the preceding mainshock is established in the form LogT = cM p + a, where "c" is a positive slope of line and "a" is function of minimum magnitude of the earthquake considered. The values of the parameters "c" and "a" are estimated to be 0.21 and 0.35 in northeast India and its adjoining regions. The less value of c than the average implies that the earthquake occurrence in this region is different from those of plate boundaries. The result derived can be used for long term seismic hazard estimation in the delineated seismogenic regions.

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“…It is important to note that unlike other magnitude scales, this scale not empirical as long as the estimate of the energy through (2) is correct. Since this magnitude is derived from either energy or seismic moment, it is often called either the energy magnitude or the moment magnitude (see also Purcaru & Berckhemer 1978, Hanks & Kanamori 1979. For earthquakes smaller than 8, M~, generally agrees with Ms, which suggests that both of the assumptions used in estimating E s from M o through (2) and relation (1) reasonable.…”

Section: Kanamorimentioning

confidence: 99%