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Source characteristics of the 1992 Nicaragua tsunami earthquake inferred from teleseismic body waves

Kikuchi, Masayuki and Kanamori, Hiroo (1995) Source characteristics of the 1992 Nicaragua tsunami earthquake inferred from teleseismic body waves. Pure and Applied Geophysics, 144 (3-4). pp. 441-453. ISSN 0033-4553. doi:10.1007/BF00874377.

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We analyzed the broadband body waves of the 1992 Nicaragua earthquake to determine the nature of rupture. The rupture propagation was represented by the distribution of point sources with moment-rate functions at 9 grid points with uniform spacing of 20 km along the fault strike. The moment-rate functions were then parameterized, and the parameters were determined with the least squares method with some constraints. The centroid times of the individual moment-rate functions indicate slow and smooth rupture propagation at a velocity of 1.5 km/s toward NW and 1.0 km/s toward SE. Including a small initial break which precedes the main rupture by about 10 s, we obtained a total source duration of 110 s. The total seismic moment is M_o =3.4×10^(20) Nm, which is consistent with the value determined from long-period surface waves, M_o =3.7×10^(20) Nm. The average rise time of dislocation is determined to be τ≈10 s. The major moment release occurred along a fault length of 160 km. With the assumption of a fault width W=50 km, we obtained the dislocation D=1.3 m. From τ and D the dislocation velocity is D=D/τ≈0.1 m/s, significantly smaller than the typical value for ordinary earthquakes. The stress drop Δσ=1.1 MPa is also less than the typical value for subduction zone earthquakes by a factor of 2–3. On the other hand, the apparent stress defined by 2μE_s /M_o , where μ and E s are respectively the rigidity and the seismic wave energy, is 0.037 MPa, more than an order of magnitude smaller than Δσ. The Nicaragua tsunami earthquake is characterized by the following three properties: 1) slow rupture propagation; 2) smooth rupture; 3) slow dislocation motion.

Item Type:Article
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Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 1995 Birkhäuser Verlag, Basel. This research was partially supported by the Grant-in-Aid for Scientific Research No. 04452067 from the Ministry of Education, Japan, the National Science Foundation Grant EAR-9303804, the U.S.G.S. grant 1434-93-G-2305. Contribution No. 5448, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125.
Funding AgencyGrant Number
Ministry of Education (Japan)04452067
Subject Keywords:Tsunami earthquake, Nicaragua earthquake, body wave inversion, source process
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Caltech Division of Geological and Planetary Sciences5448
Issue or Number:3-4
Record Number:CaltechAUTHORS:20141204-124637279
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Official Citation:Kikuchi, M. & Kanamori, H. PAGEOPH (1995) 144: 441. doi:10.1007/BF00874377
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52395
Deposited By: Tony Diaz
Deposited On:04 Dec 2014 20:56
Last Modified:10 Nov 2021 19:40

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