Singapore Seismic and Geothermal Baseline

Nicolas Eyssallenne
Dec 2, 2025
9 min read

Technical briefing by Karda One

This brief is a review of the available public studies and literature on Singapore’s subsurface. It explores what is missing for a fuller geothermal baseline, what it means for further resource exploration efforts and proposes some next steps towards de-risking Geothermal development.

1. What we know

1.1 Tectonic and seismic setting

Singapore lies on the stable Sunda Shelf, well away from active plate boundaries. Its bedrock is dominated by Triassic Bukit Timah Granite in the centre and north and Jurassic Jurong Formation rocks in the west, cut by ancient (“fossil”) faults that have shown no appreciable movement for tens of millions of years.

There is no record of a damaging earthquake originating within Singapore. All felt shaking to date comes from large regional earthquakes, principally along the Sumatra subduction zone (e.g. 2004 Aceh, 2007 Sumatra), typically at Modified Mercalli intensities III-IV and below. These events prompted the adoption of Eurocode-based seismic provisions (SS EN 1998 with National Annex) in 2013.

A small permanent network of seismographs operated by MSS, together with temporary arrays from NTU’s Earth Observatory of Singapore (EOS), confirms no detectable local tectonic seismicity over years of monitoring. The 2019 island-wide nodal survey recorded >100 “thunderquakes” and numerous construction-related signals, but no local earthquake sequence beneath Singapore itself.

The implication is that the natural seismic background is quiet. Any induced event of about M≥1–1.5 is likely to be clearly detectable instrumentally, and small felt events may be noticeable to a population that does not experience routine earthquakes.

1.2 Existing subsurface surveys and models

BCA 3D geological model

Between 2012 and 2016, the Building and Construction Authority (BCA) and partners acquired 155 km of 2D onshore seismic profiles and 170 boreholes (plus thousands of shallow boreholes) across several key areas. Seismic penetration is typically 300–500 m. These data underpin a 3D geological model covering about 40% of Singapore to a few hundred metres depth, mapping:

The distribution of Bukit Timah Granite, Jurong Formation and younger sediments.
Depth to engineering rockhead and weathered zones.
Major shallow fault zones.

The model is primarily an engineering and planning tool which constrains the upper part of any future well paths and shallow fault architecture but does not yet answer deep geothermal questions.

Island-wide nodal seismic survey

In 2019, EOS deployed 88 compact seismic nodes across the island for 40 days. Analysis using teleseismic receiver functions and ambient noise yielded:

Crustal thickness beneath Singapore of 30 to 40 km.
A clear contrast in seismic velocities across the Bukit Timah Fault Zone, confirming it as a significant crustal-scale boundary.
Detailed documentation of non-tectonic signals, including thunder-induced “thunderquakes” and human activity.

Recent work based on these data shows softer, low-velocity near-surface sediments (notably in reclaimed coastal areas) that amplify shaking, and a low-velocity anomaly beneath the Sembawang hot spring area, consistent with fractured, warm rock at depth.

Other geophysical and engineering investigations

Earlier seismic refraction studies along transport corridors, microtremor and MASW surveys, and targeted gravity and resistivity work have refined rockhead depth, weathering profiles and site response across different formations.

Extensive tunnelling (MRT lines, deep stations) and the Jurong Rock Caverns have generated a rich geotechnical dataset on:

Rock strength and deformability.
In-situ stress (including high horizontal stresses in granite).
Behaviour of fault zones and fracture networks in excavation.

Although collected for civil engineering rather than energy, these datasets provide important boundary conditions for geothermal well design and shallow casing strategies.

1.3 Evidence on heat and geothermal potential

The strongest direct evidence for geothermal potential comes from recent deep slim-holes in northern Singapore:

Admiralty: 70 °C at 1.1 km.
Sembawang: 122 °C at 1.76 km.

According to the NTU–TUMCREATE team and related reporting:

The implied gradient in the shallow part of the Sembawang area is around 70 °C/km, roughly double typical continental averages.
Simple extrapolation, supported by heat-flow estimates, suggests temperatures on the order of 200–230 °C at 4 to 5 km depth in northern Singapore, if the gradient persists downward.

Ambient noise tomography indicates a fractured, fluid-bearing zone beneath and southeast of the hot spring, further supporting the presence of a natural geothermal system at modest depths.

Taken together, existing evidence supports non-trivial geothermal potential in northern Singapore, with temperatures that may be suitable for power production at moderate depths and, potentially, for higher-temperature concepts at greater depths if conditions are favourable.

1.4 Historical exploration and nearshore context

Offshore seismic and limited petroleum exploration in the 1970s - 1980s around the Straits of Singapore and Johor Strait yielded no commercial oil or gas discoveries. Exploration ceased as it became clear that Singapore sits on a structural high with no thick, prospective sedimentary basin directly underneath.

A small number of offshore wells were drilled and found to be dry. Although these data are sparse and not fully public, they provide additional constraints on basement depth and regional structure in nearshore areas relevant to any future geothermal concepts.

This history is relevant in two ways: it confirms the absence of local hydrocarbon fields and adds to the structural picture for the upper crust in and around Singapore.

1.5 Ongoing national geothermal survey

The Energy Market Authority (EMA) has commissioned a nationwide non-invasive geophysical survey (2024–2026), being executed by Surbana Jurong. From the public documentation, methods include airborne gravity and magnetics, ground-based magnetotellurics (MT) and passive seismic.The survey aims to:

Map rock density, magnetic properties and resistivity to depths of several to 10 km.
Identify high-heat-flow corridors and favourable lithologies (e.g. radiogenic granite).
Provide a consistent national geophysical dataset for future geothermal assessments.

This programme builds directly on the Sembawang/Admiralty results and earlier EOS and BCA work and will materially improve the structural and thermal picture at depth.

1.6 Induced seismicity baseline

To date, no induced seismic earthquakes (in the sense of fault slip driven by fluid injection or extraction) have been recorded in Singapore.

Measured non-tectonic signals include:

Construction-related vibrations (tunnelling, piling, occasional blasting) with peak particle velocities kept within engineering limits.
“Thunderquakes”, shallow, thunder-induced ground rumbling recorded during storms.
Low-level signals from MRT traffic and heavy road traffic.

These observations underscore the very low ambient noise floor and provide an empirical basis for defining conservative vibration and ground-motion limits in a geothermal context.

2. What we do not know

Despite substantial existing work, several critical uncertainties remain for deep geothermal development.

2.1 Temperature structure at greater depths

Below 2 km, temperature is inferred rather than measured, and the key unknowns include:

Whether the high gradient observed at Sembawang persists to 5 km and beyond.
How thermal conductivity and heat production vary with lithology and depth (e.g. radiogenic granite vs. other units).
Whether any convective circulation (if present) alters the simple conductive gradient at depth.

These questions can only be resolved by deeper wells (5 km and beyond) with high-quality temperature logging.

2.2 Reservoir architecture and permeability

At potential geothermal exploitation depths, Singapore lacks:

Direct measurements of fracture density, orientation and connectivity in the relevant formations.
An understanding of how mapped faults and fracture swarms at shallow levels project into deeper crustal domains.
Data on natural permeability and fluid presence outside the immediate Sembawang anomaly.

This requires dedicated deep slim-holes, image logs, pressure-transient tests and, where appropriate, tracer tests.

2.3 Stress regime and fault reactivation potential

In-situ stress orientations and magnitudes at depths of several kilometres are not yet well constrained. While major faults such as the Bukit Timah Fault Zone are considered geologically inactive, their state of stress relative to frictional failure at depth under operational pore-pressure changes is unknown.

Understanding this requires:

Oriented cores and borehole image logs.
Mini-frac and extended leak-off tests.
Geomechanical modelling calibrated to new deep data.

2.4 Operational seismic thresholds (technical and social)

Technically, instrumentation is capable of detecting very small events (M<1) against a quiet background.

Socially and regulatorily, there is no established, experience-based consensus on what ground motions are acceptable beneath different land-use types (e.g. dense urban vs. industrial vs. critical infrastructure), and how often minor felt events, if any, would be tolerated.

These thresholds will need to be defined through a combination of scenario analysis, expert review, engagement with regulators and insurers, public consultation and eventually real operational data from carefully controlled tests.

2.5 Long-term performance of a deep geothermal system

The key unknowns for a power-scale system include the sustainable production rates and thermal drawdown over decades that could be assumed. Also, the chemical composition of deep fluids (if present), and implications for scaling, corrosion and materials at higher temperatures. As well as the interaction between multiple well pads in a constrained geography (pressure interference, cumulative seismic response).

These are standard questions in deep geothermal projects worldwide but they have not yet been answered for Singapore’s specific geology and urban setting.

3. What it means

3.1 A technically promising but incomplete picture

The existing baseline supports several high-level conclusions:

For the heat, northern Singapore exhibits a clear high-gradient anomaly; simple, conservative extrapolations make power-relevant temperatures at 4–5 km a realistic possibility.
For the structure, the crust is well imaged down to the Moho; major structural boundaries such as the Bukit Timah Fault Zone are known and can be built into risk assessments.
For the seismic environment, the natural hazard level is low, and the seismic noise floor is exceptionally quiet; this is helpful for monitoring but implies a low tolerance for unexpected felt events.
For the data foundation, BCA, EOS, EMA, JTC and others collectively hold extensive geotechnical and geophysical datasets that can be integrated to support geothermal planning.
The nationwide non-invasive geophysical survey (2024–2026) to evaluate the potential of up to 10km of depth is potentially a step change in support of geothermal planning.

From a subsurface physics perspective, Singapore is therefore a credible candidate for deep geothermal, but decision-grade understanding for project finance is still incomplete.

3.2 Required next steps for a bankable view

A technically robust pathway would include:

Deep slim-hole drilling in priority zones (e.g. areas highlighted by the EMA survey) to 5 km and beyond, with comprehensive logging.
Targeted reservoir characterisation:
- Image logs and core for fracture and stress characterisation.
- Injection and production tests with pressure monitoring.
Dense microseismic and deformation monitoring during any stimulation or circulation activities.

These steps are standard in modern deep geothermal practice and are necessary to refine resource estimates, confirm safe operating envelopes and support underwriting by insurers and financiers.

3.3 Seismic risk management: towards an adaptive framework

Given Singapore’s combination of:

Very low natural seismicity,
High monitoring capability, and
Dense, high-value infrastructure,

A simple, magnitude-only traffic light system (TLS) copied from other jurisdictions is unlikely to be sufficient.

A more promising framework points towards an adaptive seismic management system (aTLS) governed by a multidisciplinary technical panel, embedded in licence conditions, and supported by transparent monitoring data. The brief does not prescribe a particular design or ownership model for such a system; it highlights the technical value of more sophistication than a static red-amber-green table.

3.4 Role of existing data in de-risking future work

Existing work can already reduce uncertainty and cost for future programmes:

Well planning and shallow casing: BCA’s 3D model and tunnelling data help avoid problematic shallow zones and known near-surface faults.
Seismic network design: EOS/MSS experience provides noise baselines and identifies amplification zones, informing where to place permanent and temporary sensors.
Baseline limits and criteria: Historical vibration records from construction and the absence of natural seismicity give a practical basis for initial ground-motion and magnitude limits, to be refined as geothermal experience accumulates.

As new deep data are acquired, these public datasets can be integrated into a progressively refined subsurface and seismic picture without locking in any particular development strategy or project configuration.

About Karda One

Karda One is a Singapore-incorporated developer-integrator focused on low carbon baseload power, starting with conventional, as well as deep and superhot rock geothermal where it aligns with subsurface physics and system needs.

The company’s work centres on making deep geothermal bankable in Asian locations. This includes supporting the maturation of the industry by:

Interpreting public and project data on subsurface structure, heat and seismicity.
Framing monitoring and risk-management approaches that can be evaluated by regulators, insurers and buyers.
Designing offtake and contracting structures that allow geothermal heat and power to integrate a balanced supply mix.

Karda One does not present this brief as a development plan or siting proposal. It is intended as a technical baseline, a synthesis of existing public information on Singapore’s seismic and geothermal context, plus a transparent list of open questions that only new data and carefully staged field work can close. As further results from EMA’s nationwide survey and future deep wells are released, Karda One expects to update this note accordingly.

Indicative references

(Used as background for the brief; not exhaustive.)

Yasuda, T. et al. (2018). Development of 3D Geological Model of Singapore. JGS Special Publication 6(2): 67–72.
Dobbs, M. et al. (2022). Urban Geological Surveying in Singapore. BGS conference presentation.
Lythgoe, K. H. et al. (2020). Large-Scale Crustal Structure Beneath Singapore Using Receiver Functions from a Dense Urban Nodal Array. Geophys. Res. Lett. 47(7).
Yao, J. et al. (2025). Seismic Structure of Singapore: Implications for Tectonics and Geothermal Energy. Seismol. Res. Lett. 96(4): 2311–2323.
Straits Times (2021). First islandwide survey to uncover what lies beneath Singapore and its earthquake risk.
ThinkGeoEnergy (2024). Singapore to start two-year nationwide geothermal exploration survey.
NTU & TUMCREATE (2025). Joint press material on geothermal potential beneath northern Singapore.