Abstract: The invention relates to a micromachined accelerometer using a movable seismic mass suspended in relation to the substrate by elastic connections only allowing translation in its own plane along a sensitive axis (Oy). The mass acts on at least one elongate resonator by means of a force amplification structure associated with this resonator. The amplification structure comprises a rigid lever arm, a first end of which is connected to the seismic mass by a connection having, in the plane of the mass, a high stiffness in the direction of the sensitive axis (Oy) and a low stiffness in the perpendicular direction, and a second end is connected to an anchor point on the substrate. The second end of the lever arm is a rigid head piece surrounding the anchor point and connected to this anchor point by a rotational connection about a center of rotation.