MyShake 앱: 당신의 휴대폰을 지진계로

MyShake: Turning Smartphones into Seismometers

The MyShake application, developed at the University of California Berkeley Seismological Laboratory, demonstrates a novel approach to seismic monitoring: harnessing the collective sensing power of millions of smartphones to supplement — and in data-sparse regions potentially replace — traditional seismic station networks. Understanding how MyShake works reveals both the ingenuity of the approach and the engineering challenges involved in deploying distributed seismic sensing at global scale.

The Accelerometer at the Core

Every modern smartphone contains a micro-electromechanical systems (MEMS) AccelerometerA sensor that measures acceleration of ground motion, critical for earthquake engineering. Modern strong-motion accelerometers can record the intense shaking close to large earthquakes. — a tiny chip-scale device that measures acceleration in three orthogonal axes. These accelerometers were originally designed for screen orientation and step counting, but they also respond to ground shaking. The sensitivity of modern MEMS accelerometers is sufficient to detect moderate earthquakes (M 4.0+) at distances of tens of kilometers, though they lack the sensitivity of purpose-built SeismographAn instrument that detects and records ground motion caused by seismic waves. Modern digital seismographs can detect movements smaller than a nanometer. instruments at small magnitudes.

How MEMS Differs from Traditional Sensors

A traditional broadband SeismographAn instrument that detects and records ground motion caused by seismic waves. Modern digital seismographs can detect movements smaller than a nanometer. uses a hanging mass suspended by springs in an evacuated vault, capable of resolving ground motions as small as picometers. MEMS accelerometers have noise floors millions of times higher, limiting their effective detection threshold. However, what MEMS devices lack in individual sensitivity they compensate for in numbers — millions of devices creating a globally distributed Seismic NetworkA coordinated group of seismograph stations that continuously monitor earthquake activity. The Global Seismographic Network (GSN) includes 150+ stations providing worldwide coverage. at essentially zero marginal cost per sensor.

The On-Device Detection Algorithm

MyShake runs a lightweight machine learning classifier continuously on the phone's processor, analyzing three-axis AccelerometerA sensor that measures acceleration of ground motion, critical for earthquake engineering. Modern strong-motion accelerometers can record the intense shaking close to large earthquakes. data in real time. The classifier was trained on thousands of waveform examples to distinguish seismic shaking from human activities — walking, driving, dropping the phone — which can produce accelerations far larger than earthquake ground motion. When the on-device classifier detects a candidate seismic signal, it uploads a summary to the MyShake server without sending the complete raw waveform, conserving battery and data bandwidth.

Network-Level Earthquake Confirmation

A single phone detecting a candidate signal is insufficient for reliable event confirmation — the on-device classifier has a non-trivial false alarm rate because everyday human activities can mimic seismic waveforms. The MyShake back-end server applies a network-level algorithm that looks for spatially and temporally correlated detections across multiple devices. When dozens of phones within a geographic cluster report candidate signals within seconds of each other, the network classifier confirms an earthquake and estimates the EpicenterThe point on the Earth's surface directly above the hypocenter (focus) where an earthquake originates underground. Often reported as the earthquake's location in news reports. location and MagnitudeA single number that quantifies the total energy released by an earthquake. Each whole number increase represents roughly 31.6 times more energy released.. This two-tier approach dramatically reduces false alarm rates.

Contribution to Earthquake Early Warning (EEW)A system that detects an earthquake and sends alerts to people and systems before strong shaking arrives. Can provide seconds to tens of seconds of warning, enough to take protective action. Systems

The MyShake network has been integrated into California's ShakeAlertThe US earthquake early warning system operated by USGS and university partners. Covers the West Coast (California, Oregon, Washington) and sends alerts through Wireless Emergency Alerts. early warning system as a supplementary data source. In earthquake-prone regions with dense MyShake installations, crowd-sourced phone detections can provide an additional layer of ground truth that reduces the time to event confirmation. In developing countries where traditional Seismic NetworkA coordinated group of seismograph stations that continuously monitor earthquake activity. The Global Seismographic Network (GSN) includes 150+ stations providing worldwide coverage. infrastructure is sparse — much of South Asia, Central America, and sub-Saharan Africa — MyShake-style networks represent a low-cost pathway to basic early warning capability.

Citizen Science and Research Data

Beyond early warning, MyShake accumulates a massive dataset of seismic recordings from around the world. Researchers use this archive to study Earthquake SwarmA sequence of earthquakes occurring in a localized area over days to months with no clearly dominant mainshock. Often associated with volcanic activity or fluid injection. sequences, calibrate attenuation models in regions lacking traditional stations, and test new magnitude estimation algorithms. The app also includes a citizen science component inviting users to contribute felt intensity reports, analogous to the USGS Did You Feel It? (DYFI)A USGS program that collects intensity reports from the public after earthquakes to create community-derived intensity maps. Allows anyone who felt an earthquake to submit a report. program, creating a parallel stream of macroseismic data.

Battery and Privacy Considerations

Running a continuous sensor application raises legitimate concerns about battery consumption and privacy. MyShake is designed to minimize battery impact by activating the accelerometer only when the phone is stationary — movement detected by the gyroscope pauses seismic monitoring since a moving phone cannot distinguish seismic ground motion from user activity. Location data used for event confirmation is anonymized and aggregated on the server; individual device locations are not logged or shared. The app transmits only compact detection reports, not continuous waveform streams.

Expanding the Global Seismic NetworkA coordinated group of seismograph stations that continuously monitor earthquake activity. The Global Seismographic Network (GSN) includes 150+ stations providing worldwide coverage.

Traditional Seismic NetworkA coordinated group of seismograph stations that continuously monitor earthquake activity. The Global Seismographic Network (GSN) includes 150+ stations providing worldwide coverage. expansion is constrained by the cost of instruments (tens of thousands of dollars each), installation logistics, power supply requirements, and ongoing maintenance. A single MyShake user's smartphone provides sensing capability in a location that might otherwise be unmonitored. In subduction zone countries like Indonesia, the Philippines, and Chile, where SeismographAn instrument that detects and records ground motion caused by seismic waves. Modern digital seismographs can detect movements smaller than a nanometer. station density is insufficient for optimal Earthquake Early Warning (EEW)A system that detects an earthquake and sends alerts to people and systems before strong shaking arrives. Can provide seconds to tens of seconds of warning, enough to take protective action. system performance, MyShake-class crowdsourced networks fill critical gaps.

Limits of Smartphone Seismology

Smartphone seismology faces fundamental constraints that prevent direct equivalence with professional instrumentation. The dynamic range of MEMS accelerometers is insufficient to record both the weak early P-wave phase and the strong S-wave shaking in the same waveform without clipping. Phones placed on soft furnishings decouple from ground motion, reducing sensitivity. Phones in pockets or bags show highly variable coupling. The heterogeneity of deployment environments makes precise calibration impossible, limiting the precision of magnitude estimates derived from smartphone data alone. These limitations mean that MyShake is best understood as a force multiplier for existing networks, not a replacement.

Summary

MyShake demonstrates that the AccelerometerA sensor that measures acceleration of ground motion, critical for earthquake engineering. Modern strong-motion accelerometers can record the intense shaking close to large earthquakes. chips embedded in billions of smartphones constitute a latent seismic network of unprecedented geographic reach. By combining on-device machine learning for preliminary detection with network-level spatiotemporal correlation for confirmation, the system achieves reliable earthquake detection and Earthquake Early Warning (EEW)A system that detects an earthquake and sends alerts to people and systems before strong shaking arrives. Can provide seconds to tens of seconds of warning, enough to take protective action. capability at near-zero infrastructure cost. As smartphone penetration increases globally, crowd-sourced Seismic NetworkA coordinated group of seismograph stations that continuously monitor earthquake activity. The Global Seismographic Network (GSN) includes 150+ stations providing worldwide coverage. density will continue to grow in regions where traditional monitoring remains sparse.