Earthquake risk assessment of the Opak and Merapi-Merbabu active faults to support mitigation program in Yogyakarta province and its vicinity

Abstract

Based on historical records, Yogyakarta has a high seismic risk related to the earthquake events along active faults, such as the Opak and Merapi-Merbabu Faults. These faults were responsible for several destructive earthquakes in Yogyakarta City and its vicinity and caused fatalities and building damage in the area, e.g., the 2006 (Mw 6.3) Yogyakarta earthquake and earlier in 1943 and 1867. A previous study shows that the Opak Fault has a geodetic slip-rate of 5 mm/y and a potential magnitude Mw 6.6. In addition, the active Merapi-Merbabu Fault has a geodetic slip-rate of 1 mm/y and a potential magnitude Mw 6.6. We used scaling law relations of earthquake parameters and magnitude scenarios to estimate the recurrence time of each fault based on a kinematic model. Our results estimate that the earthquake return period (Tr) for the Opak Fault (Mw 6.6) is ∼162 years, the maximum intensity is ∼VII-VIII MMI scale, the Peak Ground Acceleration (PGA) is ∼36 % g, and Peak Ground Velocity (PGV) is ∼ 30 cm/s for a 5 km hypocentral depth. In the meantime, the earthquake return period for the Merapi-Merbabu Fault (Mw 6.6) is estimated to be ∼810 years, the maximum intensity is ∼ VI-VII MMI, the PGA is ∼ 30-36 % g, and the PGV is ∼ 21-24 cm/s for a 5 km hypocentre depth. Both faults potentially produce destructive earthquakes (Mw > 6.0) in Yogyakarta City and its vicinity. Therefore, assessments of (paleo) earthquakes are needed of both the Opak Fault and the Merapi-Merbabu Fault to support the long-term earthquake hazard mitigation program.

Engineering characteristics and classification based on JSCE in portal zones of Tunnel A, Yogyakarta - Bawen toll road, Magelang District, Central Java Province

“…Based on megascopic evaluation at the surface, the outcrop in the research area is mostly a highly weathered category [3]. Merapi -Merbabu Fault [4] is found on the right side of the tunnel. However, it was outside the 10-km radius of the tunnel.…”

Assessment of Seismic Loss in Surakarta School Buildings

“…Assuming a Poisoning distribution of the event model, the probability of exceeding each loss ratio is calculated [38]. (7) 𝜆𝜆(𝐿𝐿 > 𝑙𝑙) is the annual rate of exceeding a set of loss levels which is calculated from hazard curves combined with the vulnerability functions of the associated assets.…”

“…Surakarta city is located at the center of Java Island, (Figure 1). The city is surrounded by some potential earthquake sources such as Opak fault in the west with the slip rate of 5 mm/year, Merapi-Merbabu fault in the southwest with the slip rate of 1 mm/year, Rawapening fault in the north with the slip rate of 0.1 mm/year, and the subduction zone in the south with the movement rate of 5-7cm/year [7,8]. Unfortunately, more than 500,000 people are living in Surakarta while its area is relatively small (only 46 km 2 ), resulting in the population density of Surakarta almost 11,000 people/km 2 , higher than Semarang, the capital city of Central Java.…”

Assessment of liquefaction potential and damage on the toll road construction in earthquake-prone area, Sleman Regency, Yogyakarta

“…This earthquake killed thousands of people and destroyed much of the infrastructure in Yogyakarta and its surroundings [2]. The earthquake happened within the Opak Fault, which extends from south coast of Java Island to Prambanan, Klaten Regency [3]. The Opak fault is an active strike-slip fault that moves 5.0 mm per year [4].…”