Integral‐Rotation Linear‐Strain Model and Intraplate Deformation‐Strain Field of the Philippine Sea Plate

Abstract

AbstractIn this paper, we create an integral‐rotation linear‐strain model (IRLSM) for the Philippine Sea plate (PHIL) on the basis of the ITRF2000 velocities of 7 sites on the PHIL. Our study indicates that the current‐day tectonic motion of PHIL is a clockwise rotation, which is consistent with the rotational direction estimated by NNR‐NUVEL‐1A, but largely different from the rotational pole position and angle velocity of NNR‐NUVEL‐1A. Our model can uniformly and accurately describe the current tectonic movement and interior deformation of PHIL as compared with Sella's rigid motion model (RMM). There is an intensive deformation‐strain field within the PHIL and there is consistent eastward deformation on the plate. The deformation rate is small near the central tectonic line and large near the eastern and western boundaries, small at the southern and northern ends and large in the central part. The eastward deformation rate on the Mariana Arc is as large as 48.4mm/a. The NS‐trending deformation on the plate differs evidently in the eastern and western parts with a very small rate in the eastern part and a larger rate near the Manila Trench in the western part. The northward deformation rate at the north end is 11.3mm/a and the southward deformation rate at the south end is 29.3mm/a. The principal strain field is divided into the eastern and western areas from the central tectonic line. In the eastern area, the tensile strain is very intensive, while the compressive strain is very weak. The principal tensile strain is in near‐EW direction, the principal tensile and compressive strain rates increase gradually from the central tectonic line to the east, and the principal tensile strain rate reaches the highest value of 8.58×10−8/a near the southeast boundary (148°E, 15°N). In the western area, the principal compressive strain is very strong in a direction of NW‐SE, while the principal tensile strain is rather weak. From the central tectonic line to the west, the principal compressive and tensile strain rates increase gradually and the principal compressive strain rate reaches the maximum value of 5.71×10−8/a near the northwest boundary (122°E, 23°N). Closely related to the intraplate and surrounding tectonic settings, the spatial variation of deformation‐strain field of PHIL can be considered as a reflection of tectonic stress field.