Absolute locations of earthquakes in eastern java determined by using a minimum 1D P-wave velocity model

• Main Authors: Andinisari, Ratri, Simanjuntak, Andrean V. H., Dhanarsari, Rahadatul A. N.
• Format: Conference Proceeding
• Language: English
• Subjects: Earthquakes; P waves; Relocation; Seismicity; Subduction (geology); Travel time; Velocity; Wave velocity
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/5.0201144

The island of Java, located in the southeastern subduction zone of Australian plate beneath Eurasian, is a region rich of seismicity. Moderate to large earthquakes with magnitudes of 5.0 to 7.8 have been striking the region, making the study of its seismicity an utmost importance. Unfortunately, seismicity along the eastern part of Java has rarely been studied or assessed. This study serves as preliminary research to bridge the knowledge gap regarding the seismicity of eastern Java by performing velocity inversion and earthquake relocation. Travel times data of earthquakes that occurred in eastern Java from January 2008 to February 2022 is utilized in this inversion. Then, the newly derived P-wave velocity model is used to obtain absolute locations of these earthquakes. The resulting P-velocity model increasing slowly from 5.39 km/s at the surface down to the depth of ∼35 km. A large jump of P-velocity can also be found at the depth of 40 km, where it sharply increases from 7.21 to 7.98 km/s and keeps on increasing up to 8.39 km/s at the depth of 200 km. The absolute locations of earthquakes during the period of our study are mostly concentrated along the offshore area south of East Java. The hypocentral depths vary from the south to the north in accordance with the active subduction zone with the deepest hypocenter reaching ∼150 km. The average RMS residual of all the relocated events is 0.40 s with the horizontal and vertical errors of 9.99 and 13.64 km, respectively.