TY - JOUR
T1 - The Accumulation of Slip Deficit in Subduction Zones in the Absence of Mechanical Coupling
T2 - Implications for the Behavior of Megathrust Earthquakes
AU - Herman, Matthew W.
AU - Furlong, Kevin P.
AU - Govers, Rob
PY - 2018/9
Y1 - 2018/9
N2 - The distribution of slip during subduction megathrust earthquakes depends on the slip deficit that accumulates on the plate interface prior to the event. We develop 3-D finite element models of subduction zones to investigate how locked zones restrict surrounding regions on the plate boundary from sliding. What is new is that we quantify the slip around asperities on the megathrust. The models show plate interface slip increasing from zero at the edge of a locked zone to the relative plate motion over a distance of ~200 km along the megathrust. This area of reduced slip accumulates a seismic moment deficit up to 10 times larger than the moment deficit in the asperity alone. Updip of locked areas, slip at the trench can be reduced by more than 50% of the plate motion. Despite large displacements of the upper plate near the trench, this region moves as a semirigid block. Rupture models of the 2011 Tohoku earthquake, its tsunami characteristics, and geophysical observations near the trench can be interpreted to reflect the consequences of slip deficit accumulated on a low friction interface updip of the seismogenic zone. Neighboring asperities affect plate interface slip in a nonlinear way. Multiple asperities have overlapping pseudo-coupled regions that may restrict the magnitude of coseismic slip in single-asperity ruptures. Once an earthquake has a rupture length greater than ~250 km, it may recover the entire accumulated slip deficit. This is consistent with the magnitude of coseismic slip in several recent great megathrust earthquakes.
AB - The distribution of slip during subduction megathrust earthquakes depends on the slip deficit that accumulates on the plate interface prior to the event. We develop 3-D finite element models of subduction zones to investigate how locked zones restrict surrounding regions on the plate boundary from sliding. What is new is that we quantify the slip around asperities on the megathrust. The models show plate interface slip increasing from zero at the edge of a locked zone to the relative plate motion over a distance of ~200 km along the megathrust. This area of reduced slip accumulates a seismic moment deficit up to 10 times larger than the moment deficit in the asperity alone. Updip of locked areas, slip at the trench can be reduced by more than 50% of the plate motion. Despite large displacements of the upper plate near the trench, this region moves as a semirigid block. Rupture models of the 2011 Tohoku earthquake, its tsunami characteristics, and geophysical observations near the trench can be interpreted to reflect the consequences of slip deficit accumulated on a low friction interface updip of the seismogenic zone. Neighboring asperities affect plate interface slip in a nonlinear way. Multiple asperities have overlapping pseudo-coupled regions that may restrict the magnitude of coseismic slip in single-asperity ruptures. Once an earthquake has a rupture length greater than ~250 km, it may recover the entire accumulated slip deficit. This is consistent with the magnitude of coseismic slip in several recent great megathrust earthquakes.
KW - interseismic slip deficit
KW - megathrust earthquakes
KW - pseudo-coupling
KW - tsunamis
UR - http://www.scopus.com/inward/record.url?scp=85053918194&partnerID=8YFLogxK
U2 - 10.1029/2018JB016336
DO - 10.1029/2018JB016336
M3 - Article
AN - SCOPUS:85053918194
SN - 2169-9313
VL - 123
SP - 8260
EP - 8278
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
IS - 9
ER -