MyShakeアプリ: スマートフォンを地震計として

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) 加速度計地面の揺れの加速度を測定するセンサーで、耐震工学において重要な役割を果たす。現代の強震動加速度計は、大地震近傍の激しい揺れを記録できる。 — 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 地震計地震波によって生じる地面の揺れを検知し記録する装置。現代のデジタル地震計は、ナノメートル未満の変位も検出できる。 instruments at small magnitudes.

How MEMS Differs from Traditional Sensors

A traditional broadband 地震計地震波によって生じる地面の揺れを検知し記録する装置。現代のデジタル地震計は、ナノメートル未満の変位も検出できる。 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 地震観測網地震活動を継続的に監視する、連携した地震観測点の集合。世界地震観測網（GSN）は150以上の観測点から構成され、世界規模の観測範囲を提供する。 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 加速度計地面の揺れの加速度を測定するセンサーで、耐震工学において重要な役割を果たす。現代の強震動加速度計は、大地震近傍の激しい揺れを記録できる。 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 震央地下で地震が発生した震源の真上にあたる地表の地点。ニュース報道では地震の発生場所としてよく報じられる。 location and マグニチュード地震が放出した総エネルギー量を表す単一の数値。整数値が1増えるごとに、放出エネルギーはおよそ31.6倍になる。. This two-tier approach dramatically reduces false alarm rates.

Contribution to 緊急地震速報（EEW）地震を検知し、強い揺れが到達する前に人々やシステムに警報を送るシステム。数秒から数十秒の猶予を提供し、身を守る行動をとるのに十分な時間となる。 Systems

The MyShake network has been integrated into California's シェイクアラート（ShakeAlert）USGSと大学パートナーが運用する、アメリカの緊急地震速報システム。西海岸（カリフォルニア州・オレゴン州・ワシントン州）をカバーし、緊急速報メールを通じて警報を送信する。 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 地震観測網地震活動を継続的に監視する、連携した地震観測点の集合。世界地震観測網（GSN）は150以上の観測点から構成され、世界規模の観測範囲を提供する。 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 群発地震明確に卓越した本震を持たず、数日から数か月にわたって局地的な領域で発生する一連の地震。火山活動や流体の注入と関連することが多い。 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 「揺れを感じましたか？」（DYFI）地震後に一般市民から震度に関する報告を収集し、市民参加型の震度マップを作成するUSGSのプログラム。地震を感じた誰もが報告を投稿できる。 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 地震観測網地震活動を継続的に監視する、連携した地震観測点の集合。世界地震観測網（GSN）は150以上の観測点から構成され、世界規模の観測範囲を提供する。

Traditional 地震観測網地震活動を継続的に監視する、連携した地震観測点の集合。世界地震観測網（GSN）は150以上の観測点から構成され、世界規模の観測範囲を提供する。 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 地震計地震波によって生じる地面の揺れを検知し記録する装置。現代のデジタル地震計は、ナノメートル未満の変位も検出できる。 station density is insufficient for optimal 緊急地震速報（EEW）地震を検知し、強い揺れが到達する前に人々やシステムに警報を送るシステム。数秒から数十秒の猶予を提供し、身を守る行動をとるのに十分な時間となる。 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 加速度計地面の揺れの加速度を測定するセンサーで、耐震工学において重要な役割を果たす。現代の強震動加速度計は、大地震近傍の激しい揺れを記録できる。 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 緊急地震速報（EEW）地震を検知し、強い揺れが到達する前に人々やシステムに警報を送るシステム。数秒から数十秒の猶予を提供し、身を守る行動をとるのに十分な時間となる。 capability at near-zero infrastructure cost. As smartphone penetration increases globally, crowd-sourced 地震観測網地震活動を継続的に監視する、連携した地震観測点の集合。世界地震観測網（GSN）は150以上の観測点から構成され、世界規模の観測範囲を提供する。 density will continue to grow in regions where traditional monitoring remains sparse.