Seismic potential of Lembang fault hidden, BRIN reveals evidence

TechnonesiaID – Potential earthquake Lembang Fault is now the main concern of geologists due to its location in the northern Bandung region of West Java. Mudrik R. Daryono, a seismic geology researcher from the National Research and Innovation Agency (BRIN), provided an in-depth explanation of the structure of this large fault. The Lembang Fault is a giant crack in the Earth’s crust that functions as a very active rock movement pathway today.

The movement characteristics of this fault are dominated by leftward horizontal slip or so-called left side. This condition causes the rock blocks on the north and south sides to move in opposite directions. Even though this movement occurs slowly, a few millimeters per year, the accumulated energy can trigger serious shocks at any time.

Mudrik explained that the actual evidence of this geological activity was clearly visible in the natural landscape around Bandung. One of the most valid indicators is the change in the flow of the Cimeta River, which has moved 120 meters compared to its initial route. Indeed, at several specific observation points, the river’s displacement has been recorded as reaching 460 meters due to land movement over thousands of years.

Measuring the potential magnitude of the Lembang Fault earthquake

In addition to horizontal movement, Seismic potential of the Lembang fault also involves vertical movements or rising and falling of the ground surface. In the western part of the fault, precisely from kilometer 0 to kilometer 6, the earth’s surface tends to still appear flat. However, upon entering the next area, a striking drop appears, reaching 90 meters before finally decreasing again to the east.

Research data shows that displacement on the Lembang Fault is almost entirely dominated by horizontal movement, approximately 80 to 100 percent. Meanwhile, the vertical motion component only accounts for about 0 to 20 percent of total fault activity. This morphological change is not an instantaneous process, but rather the result of fragmentary movements that have lasted hundreds of thousands of years.

Recent research reveals that the Lembang Fault continues to move at an average speed of 1.9 to 3.4 millimeters each year. This number may seem low to ordinary people, but on a geological scale, this speed is very important for the formation of rock stresses. If this stress reaches its maximum limit, then the release of energy in the form of a large earthquake cannot be avoided.

Traces of paleoseismology and dark history of the Lembang fault

To understand to what extent Seismic potential of the Lembang faultresearchers carried out paleoseismological studies or excavated traces of ancient earthquakes. Using the method of digging test trenches at kilometer 11.5, the expert team found evidence of ground displacement of 40 centimeters in height. This discovery shows that the south side of the fault was uplifted much higher than the north side during a single seismic event.

Based on the magnitude of this change, Mudrik estimates that there have been earthquakes in the past with a magnitude of 6.5 to 7. This figure is very reasonable given that the total length of the Lembang Fault is 29 kilometers. Theoretically, the length of the fault is directly proportional to the maximum seismic force that can be produced by the geological system.

Historical geological records show that the Lembang Fault has triggered several devastating earthquakes. The most recent major event is believed to have occurred in the 15th century. Long before that, there were traces of an earthquake in 60 BC which also left a 40 centimeter deep tear in the ground. In fact, evidence of even older seismic activity has been found, around 19,000 years ago.

From this series of data, the experts concluded that Seismic potential of the Lembang fault has a recurrence cycle of between 170 and 670 years. This period provides the basis on which researchers can map future disaster risks. Knowing that the last major earthquake occurred around 500 years ago, vigilance must now be increased.

Preparing for the future seismic cycle

Referring to the calculation of the repeat cycle, Mudrik said that theoretically the next big earthquake could occur no later than around 2170. However, he provided an important note that this figure is a scientific estimate and not a precise occurrence date. In geologic time, our current position is within a cycle range relatively close to the potential for the next event.

The existence of the Lembang Fault is not just an imaginary line on a map, but a real active system on the ground. The densely populated Bandung area, including vital infrastructure such as toll roads and residential areas, is in the risk zone. Therefore, the understanding regarding Seismic potential of the Lembang fault very crucial for local governments in the formulation of land use planning policies.

This research carried out by BRIN is a scientific scenario based on modeling to deal with the worst eventuality. The main goal is not to sow fear or panic in society, but rather to serve as a foundation. disaster mitigation complete. The public is advised to start paying attention to seismic construction standards and understand evacuation routes in their respective environments.

Public education regarding disasters should continue to be encouraged so that the people of Bandung and its surrounding areas are highly prepared. By knowing the characteristics of the area where you live, the risk of loss of life and property can be minimized. Deep understanding of Seismic potential of the Lembang fault It is hoped that this will help change people’s mindset from a reactive to a preventative mindset in the face of the threat of natural disasters.