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| Illustration by Ai |
The development of Indonesia’s new capital city, Ibu Kota Nusantara (IKN) in East Kalimantan, requires a thorough understanding of geological and seismic conditions to ensure the safety and resilience of future infrastructure. A 2026 study conducted by Wira Hadi Kusuma and Harmita Lestari from Universitas Negeri Makassar revealed important seismic characteristics of the Sepaku area, one of the core development zones of IKN. The study identified four areas that require special attention due to their potential susceptibility to earthquake-induced ground deformation.
The findings are particularly
significant because IKN is being developed as a sustainable “city in the
forest.” Achieving this vision requires not only environmental preservation but
also a comprehensive understanding of subsurface conditions that can influence
how the ground responds to earthquakes. Variations in sediment thickness,
groundwater conditions, and soil properties can lead to different levels of
seismic impact even within the same region.
The IKN region is located within
the Kutai Basin, one of Indonesia’s largest sedimentary basins. Formed
through millions of years of geological processes, the basin contains thick
sedimentary deposits shaped by river, deltaic, and tectonic activities. These
complex geological conditions make local seismic assessment essential for
supporting safe urban development.
To evaluate the area, the
researchers applied the Horizontal-to-Vertical Spectral Ratio (HVSR) and
Ground Shear Strain (GSS) methods. HVSR utilizes natural ground
vibrations, known as microtremors, to determine the dominant frequency and
dynamic characteristics of near-surface geological layers. Meanwhile, GSS is
used to estimate the amount of ground strain that may occur during seismic
shaking. Microtremor data were analyzed within a frequency range of 0–20 Hz
using specialized filtering techniques to obtain reliable information about
local soil conditions.
The study found that the dominant
ground period across the Sepaku area ranges from 0.1 to 1.1 seconds,
indicating substantial variation in subsurface conditions. Areas with longer
dominant periods are generally associated with thicker or softer sedimentary
layers. Such conditions are important because they can amplify earthquake waves
and increase structural demands on buildings and infrastructure.
Researchers also calculated a seismic vulnerability index ranging from 0.001
to 0.016 s²/cm. Higher values were typically observed in locations
characterized by lower dominant frequencies and softer sediment layers.
Although the index does not directly predict building damage, it serves as an
important indicator of areas that may experience stronger local amplification
during seismic events.
One of the study’s most important findings was the identification of four
zones with high Ground Shear Strain values, approximately 0.5–0.8.
These zones may be susceptible to earthquake-induced ground deformation,
including soil compaction, slope instability, and liquefaction-related
processes. The researchers emphasized that these findings do not confirm that
liquefaction will occur. Instead, they highlight areas that should be
prioritized for more detailed geotechnical investigation.
The study also reported that the regional Peak Ground Acceleration (PGA)
in the area is relatively low, with a maximum value of about 0.05 g.
However, the authors caution that low regional seismic hazard does not
eliminate local risk. Ground conditions such as sediment thickness and soil
stiffness can significantly modify seismic waves, making local site assessments
essential for infrastructure planning.
According to Wira Hadi Kusuma and
Harmita Lestari of Universitas Negeri Makassar, the findings demonstrate that
the IKN development area should not be treated as seismically uniform.
Differences in dominant period, seismic vulnerability, groundwater conditions,
sediment thickness, and GSS values indicate that various parts of the region
may respond differently during earthquakes.
Based on these results, the
researchers proposed a three-level planning framework. The first category
includes areas with relatively favorable ground conditions that can be
developed following standard geotechnical investigations. The second category
consists of areas requiring additional studies before major infrastructure
projects proceed. The third category includes priority investigation zones
characterized by long dominant periods, high GSS values, shallow groundwater,
and greater seismic vulnerability. These locations should undergo detailed
assessments such as borehole drilling, Standard Penetration Tests (SPT), Cone
Penetration Tests (CPT), groundwater monitoring, and site-specific seismic
response analysis.
The implications of this research
are significant for the future of Indonesia’s new capital. By identifying
variations in subsurface conditions early in the planning process,
decision-makers can reduce seismic risks, improve infrastructure resilience, and
optimize long-term development costs. The study also provides an important
foundation for future seismic microzonation efforts aimed at supporting safer
and more sustainable urban development in IKN.
Author Profile
Wira Hadi Kusuma is a
researcher and academic from Universitas Negeri Makassar specializing in
geophysics, seismic site characterization, seismic microzonation, and
geological hazard mitigation. He served as the corresponding author of this
study.
Harmita Lestari is a
researcher from Universitas Negeri Makassar whose work focuses on
engineering geology and geological hazard assessment to support resilient
infrastructure development.
Research Source
Article Title: Seismic
Site Characterization and Ground Shear Strain Assessment for the Development of
Indonesia's New Capital City, East Kalimantan
Authors: Wira Hadi Kusuma, Harmita Lestari
Journal: International Journal of Applied and Advanced
Multidisciplinary Research (IJAAMR), Vol. 4, No. 8, 2026, pp. 779–792
DOI: https://doi.org/10.59890/ijaamr.v4i8.304
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