Thermal constraints on the frictional conditions of the nucleation and rupture area of the 1992 Nicaragua tsunami earthquake.

Heesemann, M., Grevemeyer, Ingo and Villinger, H. (2009) Thermal constraints on the frictional conditions of the nucleation and rupture area of the 1992 Nicaragua tsunami earthquake. Open Access Geophysical Journal International, 179 (3). pp. 1265-1278. DOI 10.1111/j.1365-246X.2009.04187.x.

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The 1992 Nicaragua earthquake was a ‘tsunami earthquake’, which generated tsunamis disproportionately large for its surface wave magnitude Ms = 7.2. Seismological studies and tsunami simulation indicated that the event was a slow earthquake, which occurred on the plate boundary between the subducting Cocos plate and the overriding Caribbean plate. We present a finite element model that enables us to estimate for the first time the temperature and inferred frictional conditions in the rupture area of a tsunami earthquake. Direct and indirect observations are used to constrain all model parameters, and surface heat-flux measurements provide independent information to verify the model results. Furthermore, we used a genetic algorithm to perform a sensitivity analysis of all model parameters and to define the spatial range of thermally defined updip limit of the seismogenic zone. The earthquake nucleated in the seismogenic zone at temperatures of ∼150 °C and propagated updip towards the trench axis. The centroid or centre of mass of moment release was located in a region characterized by temperatures of ∼50 °C. Thus, the rupture propagated through a region where plate motion is normally accommodated by aseismic creep. Our observations support a model in which tsunami earthquakes nucleate in the seismogenic zone near its updip limit. However, in such an environment coupled asperities are perhaps too small to cause large earthquakes. Seamounts, however, are abundant on the incoming Cocos plate. Therefore, in addition to temperature-dependent metamorphic induration of sediments, increased normal stress by seamount subduction may contribute to accumulate stress sufficiently large to release enough energy near the updip limit of the seismogenic zone to promote dynamic slip along a normally aseismic décollement all way to the ocean.

Document Type: Article
Keywords: Numerical solutions, Heat flow, Seismicity and tectonics, Subduction zone processes, Heat generation and transport
Research affiliation: OceanRep > SFB 574 > B6
OceanRep > SFB 574
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > SFB 574 > B5
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1111/j.1365-246X.2009.04187.x
ISSN: 0956-540X
Projects: Future Ocean, SFB574
Contribution Number:
SFB 574186
Date Deposited: 01 Dec 2009 10:24
Last Modified: 13 Jul 2018 12:15

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