This paper investigates the seismicity and rheology of the North‐Sulawesi subduction zone. Body‐wave modeling is used to estimate focal mechanisms and centroid depths of moderate magnitude (M5–M6.5) earthquakes on the North Sulawesi megathrust and surrounding region. The slip vectors of megathrust earthquakes radiate outward from Sulawesi, indicating motion that is incompatible with the relative motion of two rigid plates. Instead, the observed deformation implies lateral spreading of high topography, controlled by gravitational potential energy contrasts. This finding suggests that the observed deformation of Sulawesi results from stresses transmitted through the lithosphere, rather than basal tractions due to circulation in the mantle. Our modeling of the force balance on the megathrust shows that the subduction megathrust is weak, with an average shear stress of ∼13 MPa and an effective coefficient of friction of 0.03. Elsewhere in Sulawesi, slip vectors of other earthquakes suggest similar potential‐energy‐driven deformation is present, but at significantly slower rates. Our results show the importance of lateral rheology contrasts in determining deformation rate, and hence seismic hazard, in response to a given driving force.

中文翻译：

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苏拉威西俯冲带地壳形变与断层强度

本文研究了北苏拉威西俯冲带的地震活动性和流变性。体波模型用于估计北苏拉威西巨推力及其周围地区中度地震（M5–M6.5）的震源机制和质心深度。巨推力地震的滑动矢量从苏拉威西向外辐射，表明其运动与两个刚性板的相对运动不兼容。取而代之的是，观察到的变形暗示着高地形的横向扩展，这是由重力势能对比控制的。这一发现表明，苏拉威西岛观测到的变形是由岩石圈中传递的应力引起的，而不是由于地幔中的环流引起的基础牵引作用。我们对大推力上的力平衡进行的建模表明，俯冲大推力很弱，平均剪切应力约为13 MPa，有效摩擦系数为0.03。在苏拉威西省的其他地方，其他地震的滑动矢量表明存在类似的势能驱动形变，但速度明显慢。我们的结果表明，在确定给定驱动力的情况下，横向流变学对比在确定变形率以及由此而来的地震危险中的重要性。