Title: Hypothesis on Jerky Inner Core Rotation as the Cause of Earth's 26-Second Microseism
Author: Amit Dave
Abstract: This paper presents a novel hypothesis regarding the origin of Earth's mysterious 26-second microseism, a low-frequency seismic signal observed consistently near the Gulf of Guinea. Contrary to widely accepted theories attributing this phenomenon to ocean wave interactions, this hypothesis proposes that the Earth's inner core rotates not smoothly, but in discrete jerks of approximately 0.108333 degrees every 26 seconds. While the Earth as a whole rotates uniformly in roughly 23 hours, 56 minutes (sidereal day), the inner core is theorized to undergo periodic shifts, potentially driving the 26-second pulse observed in seismic data.The location of these microseism is at longitudes 0 degrees as well as at lattitudes 0 degrees, which supports this hypothesis.
1. Introduction The Earth exhibits a subtle but consistent seismic signal repeating every 26 seconds, detected since the 1960s. Traditional explanations focus on ocean wave resonances. However, these do not account for certain regularities and fail to explain the potential global coherence. This paper explores an alternative geophysical mechanism involving differential inner core dynamics.
2. Background Earth is composed of a solid inner core, a liquid outer core, a viscous mantle, and a solid crust. Seismic studies show the inner core may rotate slightly faster than the rest of the planet, a concept known as superrotation [1]. Yet, these findings are based on gradual, continuous motion. No studies to date have investigated the possibility of discrete, periodic jerks.
3. Hypothesis I hypothesize that the inner core does not rotate uniformly but is periodically dragged forward by 0.108333 degrees every 26 seconds. This motion might result from interactions with the fluid dynamics of the outer core or electromagnetic coupling with the mantle. Each jerk could send a low-amplitude mechanical pulse through the mantle and crust, manifesting as the 26-second microseism.
4. Theoretical Model Assuming a jerk of 0.108333 degrees per 26 seconds:
Number of jerks per day = (24 hours * 3600 seconds/hour) / 26 seconds = 3315.38 ≈ 3315 jerks
Total angular shift per day = 3315 * 0.108333 degrees = 359.999475 degrees ≈ 360 degrees
To complete a full rotation (360 degrees), the inner core would require:
Time = 360 / 0.108333 degrees = 3323.999 jerks
Time in seconds = 3323.999 * 26 = 86,423.97 seconds ≈ 24 hours
This suggests the core completes a full rotation precisely every 24 hours, matching the Earth's solar day with remarkable accuracy.
Figure 1: Graphical representation of the cumulative angular displacement of the inner core versus time, illustrating discrete steps of 0.108333° every 26 seconds resulting in one complete rotation every 24 hours.
Figure 2: Schematic of Earth's interior layers, showing possible transmission pathways of the seismic pulse from the inner core to the crust.
Mechanical Considerations:
Moment of inertia of the inner core: (approximating as a solid sphere)
Required torque: , where
Each jerk involves angular acceleration over a short time, leading to impulse-like torque signatures
5. Comparison with Observations The geographic focus of the 26-second signal near the Gulf of Guinea is not inherently contradictory. If the jerk-induced pulse travels globally but interacts constructively with oceanic or crustal structures in this region, localized amplification could occur.
6. Predictions and Tests
High-precision global seismometer arrays may detect subtle phase differences consistent with an inner-originating pulse.
Magnetometer data could reveal coupling events associated with each jerk.
Numerical models can simulate propagation from core to crust and match observed waveforms.
7. Challenges and Criticism
No direct observational evidence of inner core jerks currently exists.
Energy required for such motion may exceed plausible values unless driven by an unknown mechanism.
Must reconcile with established models of fluid dynamics and core-mantle coupling.
8. Conclusion This speculative hypothesis offers a novel mechanism for Earth's 26-second microseism, shifting focus from surface phenomena to deep Earth dynamics. While currently unverified, it suggests new avenues for research in geophysics, seismology, and planetary dynamics.
References: [1] Song, X., & Richards, P. G. (1996). Seismological evidence for differential rotation of the Earth's inner core. Nature, 382(6588), 221–224. [2] Koper, K. D., & Burlacu, R. (2015). The worldwide hum of the Earth. Nature Geoscience, 8(3), 171–172. [3] Rhie, J., & Romanowicz, B. (2004). Excitation of Earth's continuous free oscillations by atmosphere–ocean–seafloor coupling. Nature, 431(7008), 552–556.
Keywords: Inner core, Earth rotation, microseism, 26-second pulse, geodynamics, seismic resonance, core-mantle coupling
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