Hypocenter Determination and Estimation 1-D Velocity Models Using Coupled Velocity-Hypocenter Method

Abstract

Hypocenter relocation is performed to obtain a high-precision hypocenter location (accurate earthquake location). An accurate earthquake location is the key problem in seismology. Further information from an accurate hypocenter location can be used for seismicity analysis, velocity structure study, and earthquake prone mapping as one of the earthquake mitigation efforts. In this research, the method used to relocate the earthquake hypocenter was the Coupled Velocity-Hypocenter. Relocations were conducted in the Central Sulawesi region; we located 40 local earthquake events with a magnitude of ≥ 3.8 ML and a depth of ≤ 25 km. The selected P-wave traveltimes were inverted from 5 seismic stations. The variance of initial velocity models used the 1-D Primary wave velocity model of North Sulawesi, Jeffrey-Bullen and Central Sulawesi. The relocation results show that most of the hypocenters are concentrated precisely in minor faults present in the research area, and the hypocenter distribution of the events indicated as destructive shallow earthquakes occurs at depths of about 5-15 km. The residual distributions resulting from the relocation using the initial velocity model of the Central Sulawesi region indicates an improved quality if compared to Jeffrey-Bullen velocity model and the North Sulawesi velocity model, with RMS error value of 0.08 seconds. This research concluded that the 1-D velocity model in the regional (Central Sulawesi Region) reference was suitable for determining the high-precision hypocenter location.

Effect of Geometry and Number of Seismic Stations on Micro-Earthquake (MEQ) Hypocenters in Geothermal Fields

“…Coupled Velocity Hypocenter (CVH) Inversion Method is an earthquake hypocenter testing method with simultaneous station correction using the Geiger method (Kianimehr et al, 2018;Kissling, 1995Kissling, , 1998Sevilla et al, 2020;Utama, Garini, & Indrianii, 2022). The CVH method is a travel time inversion method, where the intended travel time is the difference between the seismic wave arrival time and the earthquake event time.…”

The Effect of Picking Uncertainty Window Interval on Hypocenter Micro-Earthquake (Meq) Location Using Geiger Method

“…There is no universal definition of wave arrival time, but it is generally possible to do this by manually observing the amplitude, known as the amplitudebased signal-to-noise ratio (ASNR). The arrival time is determined when a change in impulse amplitude (wave discontinuity) exceeds the noise threshold (background) on the seismogram [5,6]. The determination of the arrival time in this study was repeated 10 times as shown in Figure 4, by adjusting the width of the time window and the amplitude scale.…”

“…Primary waves arrival time (P) is one of the fundamental data in the inversion procedure, one of which is in determining the location of seismic sources. Determination of the arrival time of high-quality seismic waves contributes more to the determination of the location of the seismic source (earthquake hypocenter) with a high degree of precision [2,3], so that it can provide a big picture that truly represents the dynamic conditions of an area [1,4,5,6].…”