Using Fracture-Induced Electromagnetic Radiation (FEMR) for In Situ Stress Analysis: A Case Study of the Ramon Crater

Abstract

This study examines fracture-induced electromagnetic radiation (FEMR) to assess tectonic stress in the Ramon Crater, a geologically “stable” area in southern Israel. With its minor seismic activity, the Ramon Crater poses unique challenges for traditional methods of stress assessment. Here, we introduce FEMR as a novel approach for detecting regional stress orientations by capturing electromagnetic pulses from micro-cracks formed under stress. These FEMR pulses provide indirect but valuable indicators of stress directions on both local and regional scales, demonstrating FEMR’s capability to detect subtle stress changes even in low-activity regions. The findings show that FEMR offers a scalable and sensitive method for mapping stress orientations in stable tectonic environments, making it a promising alternative to conventional seismic techniques. This application of FEMR opens new avenues for understanding regional stress fields in areas with limited seismicity, providing critical insights into tectonic stress behaviors that influence faulting and fracture dynamics in such stable regions.

1. Introduction

1.1. The Method of Fracture-Induced Electromagnetic Radiation

The technique of fracture-induced electromagnetic radiation (FEMR) has garnered increasing interest in geosciences over the past decade due to its capability to non-invasively detect active faults and assess the directions of surface stresses in the near-surface of the Earth’s crust [1,2,3,4,5]. It is a method that can be used to infer the stress azimuth in a region by analyzing the electromagnetic signals generated during the fracturing of rocks. When subjected to differential stress above a specific limit [6], rocks develop micro-fractures and cracks. The formation and propagation of these fractures generate electromagnetic signals, which can be detected and analyzed [7,8,9]. The characteristics of the geogenic electromagnetic signals, such as their polarization and directionality, can be used to infer the orientation of the fracture planes.

Furthermore, the practical applications of FEMR are vast. Geogenic electromagnetic pulses and emissions have been used predominantly in the past decades as a precursor for earthquakes. There have been studies investigating the emission of electric and magnetic pulses minutes before earthquakes and differentiating them from seismic electric signals (SESs), which occur days to months before earthquakes. Using observations from the Grevena–Kozani earthquake (M 6.8), Varotsos et al. [10] identified a time difference (~1 s) between electric and magnetic pulse arrivals, suggesting the pulses originated from the epicentral area rather than local noise. The research links these pulses to the final stages of earthquake preparation, involving fault slip and transition from static to dynamic friction. It posits that such short-term precursors could complement longer-term SES data for improved earthquake prediction systems.

Additionally, the “natural time analysis method” has been applied to pre-fracture electromagnetic (EM) emissions to explore their critical nature in the context of earthquakes [11]. The study focuses on MHz-range EM emissions recorded prior to three significant earthquakes in Greece, revealing that these emissions exhibit characteristics of critical phenomena akin to second-order phase transitions. Potirakis et al. [11] demonstrate a strong correlation between the criticality of MHz EM emissions and foreshock seismicity, suggesting that both are manifestations of a complex system nearing failure. This reinforces the hypothesis that pre-seismic EM emissions are seismogenic and reflect the fracturing processes surrounding fault asperities.

The characteristics of geogenic electromagnetic signals, such as frequency and amplitude, are influenced by the stress magnitude and orientation [8]. This correlation helps geophysicists interpret the local or regional stress fields, which are crucial for understanding tectonic activities, fault behavior, and earthquake potential. The dominant orientation of the fractures can be used to comprehend the principal stress directions since the stress field influences the fracture orientation in the region [3,4,5]. The fractures that generate electromagnetic radiation will form in a direction that minimizes tensile stress, which typically aligns with the current stress field in the region. The stress azimuth (the maximum principal stress direction) can be inferred by mapping these fracture orientations and correlating them with the stress field. Using a portable FEMR measurement device, it was demonstrated that for field measurements, the direction of lithospheric stresses is often related to the direction of principal FEMR emission [1,3,5].

The FEMR technique was utilized to calculate the stress azimuth in the Upper Rhine graben, a major rift extending for approximately 300 km in Central Europe. The horizontal stress was oriented N–S to NNE–SSW, which differs from the azimuth trending in the NNW–SSE direction using tectonic models and focal plane mechanisms. This was attributed to stress rotation of the maximum horizontal stress between depth and near-surface [12]. Mallik et al. [3] used the technique of FEMR to determine the directions of horizontal principal stresses and identify active faults in the Kachchh region of India, known for its high seismicity. The study revealed an azimuth of N60°E and compared its deviation from the regional stress obtained from focal plane solutions. Das et al. [5] utilized the technique of FEMR to determine the horizontal stress azimuth along 18 locations across the Narmada–Son lineament (NSL), a part of the Central Indian Tectonic Zone (CITZ). The orientations varied between N15°E and N170°E, with a mean azimuth of N85°E. The study also compared the results obtained from earthquake focal point mechanisms, borehole data, and hydrofracturing data to display a deviation from the NNE–NNW trending regional stress and realignment along the E–W trending NSL. The maximum stress azimuth parallel to the NSL proves the NSL is tectonically active. This technique has been used to decipher the direction of recent near-surface stresses along specific segments of the major thrusts along the Darjeeling–Sikkim Himalayas [5]. It was subsequently used to find the magnitude of horizontal stresses and the determination of stress regime in a region inside the tectonically active Rangit Window [5].

The FEMR method has demonstrated its effectiveness in determining in situ stress directions, offering a non-invasive and efficient approach to 3D stress measurements. Previous studies have shown the reliability of FEMR signals, even under challenging conditions [13,14]. Our study focuses on the Ramon Crater (Figure 1), a region shaped by a complex tectonic history at the convergence of multiple tectonic plates. By applying FEMR to investigate ongoing tectonic adjustments, this research aims to evaluate the stability and evolution of the local stress field, further validating FEMR as a robust tool for geophysical analysis. In this context, FEMR is positioned as a novel remote sensing method that provides critical insights into subsurface geodynamic processes. Its ability to detect and map subtle stress variations and fracture networks enhances our understanding of geological structures in relatively stable regions. By integrating FEMR data with traditional geological mapping, this study enables multi-scale analysis of residual stress fields, addressing both local and regional dynamics.

Our work contributes to the advancement of remote sensing applications by tackling the challenges associated with relatively inactive tectonic areas. The findings have broader implications for geohazard assessment, resource management, and interdisciplinary research across geophysics, structural geology, and tectonic evolution. By showcasing FEMR’s potential to extract detailed, non-invasive geodynamic information, this study reinforces the role of remote sensing in developing innovative approaches to complex geological and environmental problems.

1.2. Stress Indicators and Stress Measurements in the Field

The stress regime in southern Israel is determined by studying various geological stress indicators, which provide insights into the orientation and evolution of the regional stress fields. These indicators include joint sets, faults, dikes, folds, and earthquake focal mechanisms.

Joint sets, which form in response to tectonic stress, are key indicators of stress orientation. In southern Israel, four main joint set orientations, WNW–ESE, NNW–SSE, NE–SW, and NW–SE, have been identified, corresponding to the regional stress regimes. The most significant orientations are WNW–ESE, aligning with the Syrian Arc Stress (SAS), and NNW–SSE, reflecting the Dead Sea Stress (DSS) [16]. NNW–SSE joints cutting across WNW–ESE joints are examples of when the DSS overprinted the earlier SAS structures.

Faults and dikes are additional stress indicators that help determine the direction of tectonic forces. Significant strike-slip faults aligned with the Dead Sea Transform (DST) reflect the extensional forces associated with the DSS (Figure 1 and Figure 2). In contrast, fault planes can provide estimates of the orientation of maximum compressive stress (SH_max) and minimum stress (SH_min) [17]. Dikes, which typically form parallel to SH_max, also indicate the stress field during their emplacement. In southern Israel, dikes from the Miocene show both NNW–SSE (DSS) and WNW–ESE (SAS) alignments, reflecting the alternating influence of these stress regimes [18].

Tectonic stylolites, formed under compressive stress, are aligned with SH_max and provide further evidence of historical compressional forces. Stylolites aligned with WNW–ESE confirm the presence of SAS-related compressional stress in southern Israel [17]. Additionally, earthquake focal mechanisms are crucial in determining current stress directions. Data from earthquake focal plane solutions in the Dead Sea region consistently indicate NNW–SSE compression and ENE extension, characteristic of the DSS regime [20].

Fracture Spacing and Layer Thickness: The relationship between fracture spacing and mechanical layer thickness is another method used to infer stress regimes. In southern Israel, DSS-related joints tend to have closer spacing, suggesting more significant extensional strain than those associated with the SAS [21]. This allows geologists to estimate the relative intensity of different stress fields and their geological impacts.

2. Materials and Methods

2.1. Brief Geological Background

The Ramon Crater (“Makhtesh” Ramon in Hebrew) in southern Israel offers a vivid record of geological processes. The most giant erosion crater in the world (approximately 40 km long and up to 10 km wide, shaped like an elongated heart, Figure 2), is located in Israel’s Negev Desert, part of the larger Arabian plate. Situated on the Ramon anticline, part of the Syrian Arc fold belt, tectonic activity has significantly influenced this area. The broader geological context includes the Neqarot syncline and the Ramon fault zone, which are critical to interpreting the tectonic evolution of the region [18]. This natural wonder formed around 220 million years ago when oceans covered the area. As the sea receded, rock layers eroded, leaving behind the dramatic, multi-colored landscape seen today. The Ramon Fault is a significant structural feature running along the length of the crater. It has influenced the crater’s formation and evolution by controlling the direction of erosion and the collapse of rock layers [22,23]. Its landscape, shaped by volcanic and sedimentary forces, features a complex system of over 200 basaltic and trachytic dikes. These dikes, primarily arranged in a radial pattern with additional NW–SE and NE–SW trends, reveal the area’s rich volcanic history [18]. Volcanic activity in the region peaked around 120 million years ago during the Middle Cretaceous, driven by upper-mantle hot spots. This period was marked by explosive volcanism, which produced central-type volcanoes, lava flows, eruptive breccia, and tuffs. Magmatic processes occurring before and after the sub-Cretaceous unconformity were instrumental in shaping the area’s geological evolution [24]. The uplift of the Ramon anticline, which took place approximately 60–70 million years ago along the Ramon fault, exposed essential sedimentary layers such as chalk and flint. These layers provide crucial clues about the region’s tectonic and sedimentary history. In the last 20 million years, erosion, primarily due to river action, has carved softer sandstone layers, leading to the distinctive topography of the crater [25].

The Arod volcano, which consists of basanitic–nephelenitic rocks and is surrounded by tuffs and lava flows, further highlights the region’s volcanic heritage. Its activity, along with the formation of second-order folds and flexures in conjunction with the dikes and sills, showcases the complex interplay between tectonic and magmatic processes that have shaped the landscape [25].

The surrounding region also exhibits a variety of joint sets, especially in the Gerofit Formation, which align with the regional stress fields associated with the Dead Sea Transform and Syrian Arc structures. Studying these joint sets is crucial for understanding the tectonic forces that have shaped the region over millions of years [26].

2.2. Stress Regime in Southern Israel

The stress regime in southern Israel is influenced by the interaction of two major regional stress fields: the Syrian Arc Stress (SAS) and the Dead Sea Stress (DSS). These fields have developed over millions of years and have been instrumental in shaping the region’s tectonic and geological features [16,17,18,20,21,22,23,24,25].

The SAS field has been active since the Late Cretaceous and is oriented WNW–ESE. This compressional stress is linked to the collision of the African and Eurasian plates and has led to large-scale folding and faulting structures throughout southern Israel. The Syrian Arc fold belt, extending from northern Sinai through Israel into Syria, is a prime example of the structures formed under SAS. Notable features, such as the Ramon anticline, have also been shaped by this compressional stress [18]. The WNW–ESE-oriented joint sets in many sedimentary layers, particularly in Upper Cretaceous carbonates, are vital indicators of SAS-related tectonic activity [27].

The DSS field arose during the Middle Miocene with the Dead Sea Transform (DST) development, a left-lateral strike–slip fault marking the boundary between the African and Arabian plates. The DSS is oriented NNW–SSE and has overprinted the earlier SAS structures, introducing extensional forces perpendicular to the Dead Sea Transform. This extensional stress is evident in developing NNW–SSE-aligned joint sets, particularly in the Gerofit Formation and other rock units in the central Negev [16]. These joint sets and faults reflect tectonic strain due to movement along the DST.

The interaction between the SAS and DSS fields has led to a complex stress regime in southern Israel. The DSS dominates near the Dead Sea Transform (DST), which runs along the boundary between the Arabian and African plates. Both fields have influenced the region’s tectonic history. Alternating periods of dominance between the two regimes have resulted in joint sets with WNW–ESE (SAS) and NNW–SSE (DSS) orientations. This combination of compressional and extensional phases has created a dynamic and diverse geological environment [28].

2.3. Instrumentation and Data Processing

The FEMR data are collected using a portable instrument called ANGEL-M, manufactured by JSC, VNIMI, Russia [5,14,15]. This device measures electromagnetic radiation from rock fracturing on the Earth’s surface and underground/mining. It includes three ferrite antennas, a receiver, processors, a converter, and storage components. The device can measure frequencies from 5 to 150 kHz with high sensitivity. To minimize interference, measurements are taken with the antennas placed in three orthogonal directions, usually for 10 s. However, anthropogenic (human-made) signals can interfere with natural data, so monitoring is conducted away from electrical sources to ensure accurate results. This is detailed in [14,15].

This instrument uses a high-pass filter to improve the signal-to-noise ratio, making distinguishing between geogenic and anthropogenic electromagnetic signals (FEMR) easier. The study filtered out noise from anthropogenic sources using several filters, including a noise removal filter, a biquad notch filter, and a Chebyshev filter, significantly improving data quality [15]. Signal processing was conducted to calculate parameters like amplitude and frequency for each FEMR pulse. The methodology was tested and validated in the field (Eilat region and Dead Sea Basin) and the lab, confirming the theoretical basis of FEMR signal propagation [14,15].

2.4. Calculation of Stress Azimuth

Figure 3 displays the schematic representation of an electric field in a 3D manner to calculate the corresponding stress azimuths for each monitoring location. The stress azimuth is calculated by representing the electromagnetic field vector emanating from microcracks in a 3D Cartesian coordinate system. The analysis uses the amplitudes of the electric fields in three orthogonal directions, captured by antennae aligned with the north, west, and vertical directions. These components are mathematically projected into a spherical polar coordinate system to compute the azimuth of the stress field. The conceptual framework of this methodology is to calculate the stress azimuth by leveraging the electric field vectors generated by microcrack activity in rocks.

When stress builds up in a rock mass, microcracks propagate, generating geogenic electromagnetic radiation. The electric component of this radiation is recorded in three orthogonal directions:

• North–south (Ex);
• West–east (Ey);
• Vertical (Ez).

These electric components are treated as Cartesian coordinates (Ex, Ey, Ez) and are projected onto a spherical polar coordinate system to derive the azimuthal angle of the electromagnetic emissions. The spherical polar transformation involves the azimuthal angle (φ), which indicates the horizontal direction of the E-field, derived using trigonometric relationships between Ex and Ey. On the other hand, the polar angle (θ) represents the vertical inclination of the electric fields, involving Ez and the horizontal field’s magnitude. FEMR outputs arise from charge separation and recombination during microcrack formation. This process generates electromagnetic waves, including measurable electric field components. The FEMR outputs in the form of electric field measurements are processed to determine the direction of the maximum electric field, which is linked to the stress orientation. This is because the azimuth correlates with the direction of the principal stress (σ₁) since microcrack propagation aligns with the local stress field. This enables the estimation of the stress azimuth directly from the electromagnetic data by enabling FEMR to act as a proxy for mapping stress azimuths.

Hence, the 3D representation in the Cartesian coordinate system of the geogenic electromagnetic field emanating from the microcracks is:

$$\dot{\overrightarrow{E}=E_1}\widehat{x}+E_2\widehat{y}+E_3\widehat{z},$$

(1)

Hence, the amplitude of the above electric field vector is the signal’s amplitude. This can be written as:

$$‖E‖=\sqrt{(E_1^2+E_2^2+E_3^2)},$$

(2)

E₁, E₂, and E₃ are the electric fields in the x, y, and z directions, respectively. Correlating them with the data acquisition methodology in the field area, the subscripts 1, 2, and 3 represent the orthogonally oriented antennae, which are aligned in the north, west, and vertical directions, respectively. Hence, E₁, E₂, and E₃ are the electric fields obtained from antennae channels 1, 2, and 3, respectively.

According to the vector analysis, we can say the following:

$$\cos \alpha ={\displaystyle \frac{E_1}{‖E‖}}, \cos \beta ={\displaystyle \frac{E_2}{‖E‖}}, \cos \gamma ={\displaystyle \frac{E_3}{‖E‖}},$$

(3)

$$\alpha =\arccos \left({\displaystyle \frac{E_1}{‖E‖}}\right), \beta =\arccos \left({\displaystyle \frac{E_2}{‖E‖}}\right), \gamma =\mathrm{a}\mathrm{r}\mathrm{c}\mathrm{c}\mathrm{o}\mathrm{s}\left({\displaystyle \frac{E_3}{‖E‖}}\right)$$

(4)

Now, to calculate the stress azimuth (ϕ), the above Cartesian representation of the electric field vector ($\overline{E}$) needs to be projected to the spherical polar coordinate system (Figure 3).

$$\varphi =\arctan ({\displaystyle \frac{y}{x}}) \mathrm{or}, \mathrm{in} \mathrm{our} \mathrm{case}, \arctan ({\displaystyle \frac{E_2}{E_1}}),$$

(5)

3. Results

FEMR Rose Diagrams

Rose diagrams were plotted based on calculating the horizontal stress azimuth obtained from the nine field locations (Figure 4 and Figure 5). As the microcracks generate FEMR, their orientation indicates where the maximum EMR emission occurs [14,15].

4. Discussion

4.1. Comparison of the FEMR Data with the Stress Regime in the Ramon Crater Area

Field studies in the Ramon Crater area have identified key stress indicators, including joint sets, fault planes, and dikes [16,17,18,20,21,22,23,24]. Measurements of joint sets reveal two dominant orientations: WNW–ESE (282 ± 5°), consistent with the SAS field, and NNW–SSE (345 ± 5°), associated with the DSS field [13]. These orientations are found across multiple geological units, indicating the long-term influence of both stress regimes [17]. Earthquake focal mechanisms also support the NNW–SSE extensional stress direction, confirming the ongoing influence of the DSS [20].

Hence, the stress regime in the Ramon Crater area is shaped by the combined influence of the SAS and DSS fields. These two fields have played a significant role in the region’s tectonic evolution, creating a complex pattern of stress orientations. As was noted above, the WNW–ESE-oriented SAS field has been a major factor in the formation of tectonic structures in the Ramon Crater area. This compressional stress regime, active since the Late Cretaceous, is responsible for features such as the uplift of the Ramon anticline and the deformation of surrounding sedimentary layers [18]. Joint sets aligned WNW–ESE are widely distributed throughout the region, particularly in Upper Cretaceous carbonates, indicating the long-term compressional influence of the SAS [28]. During the Middle Miocene, the development of the DSS field produced NNW–SSE-oriented extensional forces in the Ramon Crater area. This extensional stress overprinted earlier SAS structures and produced new joint sets and fault orientations aligned NNW–SSE [16]. The DSS has created a pattern of normal faults, extensional fractures, and joint sets across the region. The superimposition of the DSS and SAS fields has resulted in a complex tectonic environment in the Ramon Crater. The SAS has primarily produced compressional features such as folds and anticlines, while the DSS has introduced extensional structures such as normal faults and joints. In some locations, NNW–SSE joints from the DSS are observed cutting across WNW–ESE joints from the SAS, demonstrating that the DSS is younger and has progressively modified the earlier SAS-related structures [28].

The FEMR results yielded a mean stress azimuth of 307.99 ± 2.32 based on the data collected and analyzed from the nine monitoring locations along the Ramon Crater (

Table 1. The rose diagrams of the calculated FEMR (Equations (3)–(5)).

Location	Latitude/ Longitude	Rose Diagram	Calculated Azimuth	Standard Deviation	Strike
1	30.615250/ 34.839111		65	12.99	N295°E
2	30.620694/ 34.843361		51	−1.007	N309°E
3a	30.605333/ 34.866750		59.29	7.282	N301°E
3b	30.603361/ 34.872111		53.29	1.280	N307°E
4	30.598500/ 34.866889		48.44	−3.563	N312°E
5	30.592738/ 34.888841		40.60	−11.404	N319°E
6	30.57539/ 34.87761		49.75	−2.258	N310°E
7	30.594639/ 34.886833		52.67	0.661	N307°E
8	30.59583/ 34.876167		48.02	−3.983	N312°E

). This was calculated based on the “calculated azimuth” column in Table 1. Based on the sections above, we know several regional stress indicators. One is the two dominant orientations of the joint sets, i.e., WNW–ESE (282 ± 5°) and NNW–SSE (345 ± 5°), corresponding to the SAS and DSS fields. Hence, we can conclude that the results from the FEMR analysis yielded stress, which is approximately equal to the acute bisector of the two joint sets (313.5 ± 5°). This result is consistent with the direction of the least principal stress (±3).

The fact that the stress azimuth is nearly equal to the acute bisector suggests that σ₁ is significantly influenced by the orientation of the joint sets [30]. It also implies that the current stress field is relatively stable, reflecting a stable tectonic environment where previously formed joints still respond to the present stress. Moreover, the acute bisector is representative of the least principal stress (σ₃) and hence signifies where new fractures are likely to form. It indicates regions of potential weakness in the rock bodies where additional fracturing could occur under the current or future stress conditions.

The other stress indicator in the region is the numerous dikes in the Ramon Crater, which can be attributed to the region’s erosional history [16] combined with tectonic extensions, magmatic intrusions, and fracture networks. Due to the influence of the SAS and its resulting tectonic extension, fractures and faults were created in the region [28]. Dikes were formed when the magma from below the surface intruded into these fractures. The extension of the crust creates space for magma to flow into, resulting in dikes that often follow the direction of the minor principal stress (σ₃). The region has a history of magmatic activity, especially during periods of tectonic stress. The dikes are essentially vertical or near-vertical sheets of igneous rock injected into pre-existing fractures during volcanic or tectonic activity periods. In the Ramon Crater, dikes are mostly basaltic in composition, suggesting that the source of the magma was deep in the mantle, and it found pathways through the fractured crust due to tectonic movements [16]. The area contains numerous faults and fractures, which serve as pathways for magma intrusion. The Ramon Crater is not only a result of erosion but is also shaped by complex structural geology, where previous tectonic events have weakened the crust [18]. Well-defined joint sets provide natural conduits for magma to travel through [31]. When magma rises from deep below, it preferentially moves along these weaknesses, forming dikes aligned with the prevailing stress regime.

Figure 5 shows that the dikes’ orientation is approximately parallel to the stress azimuth in the region, as analyzed from the rose diagrams. This, in turn, indicates that these dikes are oriented parallel to the acute bisector, suggesting that the fractures that allowed for dike intrusion were influenced by the same stress regime that governs the joint sets. The alignment of the dikes with the acute bisector implies that they were likely formed in response to the same maximum principal stress direction that governs the current joint sets. This indicates that the stress field during dike formation was similar to the current stress conditions, suggesting a relatively stable tectonic environment over time.

Hence, the two regional stress indicators, the joint sets and dikes, bridge a coherent relationship between tectonic stress, fracture formation, and magmatic intrusion.

4.2. The Reason for FEMR Excitation in a “Stable” Stress Field

The Negev desert, including the Ramon Crater, is primarily influenced by the DSS and, to some extent, by the SAS [16]. The Dead Sea Transform (DST) is a major left-lateral sinistral strike–slip fault system that runs along the boundary between the African and Arabian plates [27,32].

This transform fault enables the Arabian plate to move northward relative to the African plate at a rate of 1 mm/year–5 mm/year [28,32,33,34]. This shear stress along the DST is responsible for the deformation and seismic activity in the Dead Sea Region. The opening of the Red Sea Rift is an aftereffect of the strike–slip movement along the DST caused by the northward movement of the Arabian Plate as it diverges from the African Plate. This movement leads to both lateral shear and extension stresses in nearby regions like the Ramon Crater, which, in turn, influence the faults, joints, and dike formations [29,31].

On the other hand, the SAS was initially formed due to compressional forces as a response to the collision of the African plate with the Eurasian plate during the Late Cretaceous period [28], which in turn led to a lithospheric shortening of 5 mm/year and increasing to 40 mm/year in active subduction zones [34,35]. This stress field led to the formation of the Syrian Arc fold and thrust belt, affecting Egypt, the Negev Desert, and parts of southern Israel. Although the Syrian Arc System originated as a compressive structure, the stresses in this area have since been modified by the interaction between the African and Arabian plates. The current stress field in the Syrian Arc region has been influenced by the relative movements along the Dead Sea Transform fault and the opening of the Red Sea. These tectonic forces have added a strike–slip and extensional stress component to what was initially a compressional stress regime. In the Negev, including the Ramon Crater, the Syrian Arc stress created folds, faults, and uplifts that can still be observed in the region’s topography. Though the Syrian Arc stress is an older tectonic event, it set the foundation for much of the structural framework in the Negev, including some of the arching and uplift seen in the Ramon Crater. However, its current influence is minimal compared to the more active DST.

Hence, the Ramon Crater is primarily influenced by Dead Sea Transform stress, which generates strike–slip and extensional forces shaping the region’s current faulting, jointing, and dike patterns. The Syrian Arc stress historically contributed to the structural framework but played a lesser role in ongoing deformation. These stresses help explain the unique landscape, fractures, and geological structures observed in the Ramon Crater and the broader Negev Desert [16,18,29]. Hence, it is not “dynamic” in terms of earthquakes. However, the stress field changes due to the relative movement of the tectonic plates. The FEMR technique detects this regional stress.

FEMR pulses correspond to a region’s stress field by detecting the localized stress release within fractures and micro-cracks, which can be linked to the regional stress orientation and intensity. FEMR pulses are emitted when rocks under stress develop or propagate micro-cracks, whose formation and orientation depend on the region’s principal stress directions. In areas like the Ramon Crater, micro-crack alignment often correlates with the regional stress azimuth [26]. When stress is applied to rocks, new micro-cracks typically form perpendicular to the minimum principal stress (σ₃). As these cracks develop, FEMR pulses are released, which can indicate the stress orientation causing these micro-cracks [8]. Moreover, FEMR pulses will tend to increase along the direction with the highest stress concentration or specific fractures aligned with the principal stress [2,3,5]. For example [5], the alignment of the stress azimuth along the tectonically active Narmada–Son Lineament was demonstrated as part of the Central India Tectonic Zone (CITZ). Since this region experiences intracontinental earthquakes regularly, “local stresses” contribute to the change in the stress azimuth along the fault escarpment. Subsequently, the stress azimuth corresponds to the regional stress as we move farther away from the active faults [5]. Similar case studies are observed in the Kachchh region, where local stresses affect the stress azimuth when measured close to the vicinity of the Kachchh Mainland Fault (KMF) and the South Wagad Fault (SWF). Subsequently, the regional stress azimuth is dominant when measurements are taken at a considerable distance from the two active faults in the region [3].

Hence, FEMR is a viable technique for determining regional and local stress azimuths. It can capture stress orientation on multiple scales due to its sensitivity to micro-crack activity and fracture reactivation, which reflect the stress state acting on rocks. Even when a region undergoes minor stress redistribution (typically associated with stable areas), certain fractures within the regional fracture network can undergo small-scale reactivation. This reactivation generates FEMR pulses. The orientation of these reactivating fractures is often aligned with the regional stress field, meaning the pulses give indirect evidence of how stress is redistributed within the fracture network. For example, if FEMR pulses primarily come from fractures oriented along a specific azimuth, it indicates alignment with the prevailing regional stress direction. As mentioned in Section 1.2, the Ramon Crater is a comparatively “stable” region and does not experience periodic earthquakes. Hence, we observe here that the FEMR technique is a viable tool for determining the regional stress of the area attributed to the plate movements contributing to the DSS and SAS.

5. Conclusions

The structural characteristics and stress patterns within the Ramon Crater are primarily governed by tectonic forces from the Dead Sea Transform (DST) and, to a lesser extent, historical contributions from the Syrian Arc System (SAS). While the DST imposes strike–slip and extensional stresses due to the northward movement of the Arabian plate, the SAS’s initial compressional forces laid the region’s foundational topography and structural framework. The Ramon Crater landscape thus reflects a unique intersection of ancient and ongoing tectonic forces, making it an exceptional study area for geological and stress-field analyses.

Applying the FEMR method in studying regional and local stress orientations here represents a novel approach. Unlike conventional stress measurement techniques, FEMR’s sensitivity to micro-crack activity enables it to detect stress orientations on multiple scales, offering a more dynamic, real-time understanding of how stress is distributed and redistributed across the fracture network. FEMR pulses correlate with micro-crack formation, providing insight into regional and localized stress orientations, even in tectonically “stable” areas like the Ramon Crater. This precision allows FEMR to detect subtle stress shifts that might otherwise go unnoticed with standard tools, adding depth to our understanding of how the current stress field is organized.

However, while FEMR’s ability to monitor small-scale stress changes is advantageous, it may also be sensitive to transient stress variations not indicative of long-term tectonic trends. Moreover, interpreting FEMR data requires careful correlation with established tectonic models to avoid overestimating minor stress redistributions. Overall, FEMR enhances our capacity to assess the active stress fields in regions shaped by ancient tectonic forces, advancing our knowledge of regional geodynamics.