# Tsunami Arrival Detection with High Frequency (HF) Radar

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## Abstract

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## 1. Introduction

## 2. Detection of the Tsunami Signal in HF Radar Data

- For band b at time t, calculate the average a
_{b}(t) and standard deviation s_{b}(t) of the velocity v_{b}(t) over the preceding hour. - For each band, calculate a measure of the velocity deviation from the background$${d}_{\text{b}}(\text{t})=\frac{({\text{v}}_{\text{b}}(\text{t})-{\text{a}}_{\text{b}}(\text{t}))}{{s}_{\text{b}}(\text{t})}$$The velocity deviation function D(t) at time t is defined to be the product over the bands:$$D(\text{t})=\prod _{b}{d}_{\text{b}}(\text{t})$$
- For each band, calculate the change in velocity over two adjacent time intervals from t − 2δ to t, where δ is the time resolution of the input data:$$\Delta {\text{v}}_{\text{b}}(\text{t})={\text{v}}_{\text{b}}(\text{t})-{\text{v}}_{\text{b}}(\text{t}-1\delta )$$The velocity increment function ΔV(t) is defined to be the sum over the bands:$$\mathrm{\Delta}V(\text{t})=\sum _{\text{b}}\mathrm{\Delta}{\text{v}}_{\text{b}}(\text{t})$$
- Calculate a correlation function C(t) describing the correlation between velocities in three adjacent bands over times t, t − δ, t − 2δ, where δ is the time resolution of the input data. The correlation function C(t) is set to unity, unless the velocity increases or decreases with time for all three area bands from t − 2δ to t − δ, and t − δ, to t, when it is defined to be 100.
- The tsunami detection factor at time t is defined to be the product of the correlation function, the velocity increment function and the velocity deviation function:$$\text{q}(\text{t})=\text{C}(\text{t})\cdot \mathrm{\Delta}\text{V}(\text{t})\cdot \text{D}(\text{t})$$

## 3. Application to Radar Data

#### 3.1. Japan

#### 3.1.1. Kinaoshi, Hokkaido (A088)

#### 3.1.2. Tokushima, Japan (TOKU)

#### 3.2. US West Coast

#### 3.2.1 Yaquina Head South, Oregon (YHS2)

#### 3.2.2 Point Estero, California (ESTR)

#### 3.3. Comparison between Arrival Times Measured by Radar and Tide Gauge

## 4. Conclusions

## Acknowledgments

## References

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**Figure 1.**Radial current velocities from the Usujiri, Hokkaido radar and the area bands used in the analysis which are 2-km wide and approximately parallel to the depth contours.

**Figure 2.**Time series of current velocity components from the Kinaoshi radar. Radial current velocities were resolved perpendicular to the area band boundaries, and averaged. Area bands used were 2 km wide and approximately parallel to the depth contours. Blue: 6–8 km; Red: 8–10 km; Black: 10–12 km. (

**a**) From 2 h before the quake until 5 h after. (

**b**) Around the tsunami arrival.

**Figure 3.**Time series of averaged velocity components showing the typical appearance around the tsunami arrival for three adjacent 2-km area bands. (

**a**) A087 (Hokkaido, Japan, JST); (

**b**) YHS2 (OR, USA, UTC); (

**c**) BML1 (CA, USA, UTC); (

**d**) PREY (CA, USA, UTC).

**Figure 4.**(

**a**) The general location of the Japan earthquake and the radars in Hokkaido and on the Kii Strait. Both locations were sufficiently far from the epicenter to experience only moderate disturbances. (

**b**) The bathymetry offshore from the Radars A088, A087 on the Kameda Peninsula, Hokkaido and the tide gauge at Hakodate. (

**c**) The bathymetry offshore from the Radars TOKU, ANAN on Shikoku and the KO seabed wave gauge.

**Figure 5.**Time series of velocity components from radar A088. (

**a**) Blue: 0–2 km; Red: 2–4 km; Black: 4–6 km over 5 h (

**b**) q-factor for 0–6 km offshore (

**c**) Blue: 6–8 km; Red: 8–10 km; Black: 10–12 km (

**d**) q-factor for 6–12 km offshore.

**Figure 6.**Time series of velocity components from TOKU. (

**a**,

**b**): Blue: 0–2 km; Red: 2–4 km; Black: 4–6 km; Green 6–8 km (a) over 10 h (b) around the tsunami arrival time (

**c**) Blue: 8–10 km; Red: 10–12 km; Black: 12–14 km; Green 14–16 km. (

**d**) q-factor for 2–8 km offshore.

**Figure 7.**The location of the radars and tide gauges on the US West Coast, and the offshore bathymetry.

**Figure 8.**Time series of velocity components from radar YHS2 (

**a**) Blue: 2–4 km; Red:4–6 km; Black: 6–8 km (

**b**) q-factor for 2–8 km (

**c**) Blue: 8–10 km; Red: 10–12 km; Black: 12–14 km (

**d**) q-factor for 8–14 km offshore.

**Figure 9.**Time series of velocity components from radar ESTR (

**a**) Blue: 2–4 km; Red: 4–6 km; Black: 6–8 km (

**b**) q-factor for 2–8 km offshore (

**c**) Blue: 8–10 km; Red: 10–12 km; Black: 12–14 km. (

**d**) q-factor for 8–14 km offshore.

Japan 11 March 2011 JST | ||||
---|---|---|---|---|

Radar (XMTR Freq) | Arrival Time (JST) | Ground Instrument | Arrival Time (JST) | Water-Level Change |

A088 (42Mhz) | 15: 49 | Hakodate tide gauge | 16:32 | 2.0 m |

A087 (42Mhz) | 15: 54 | Hakodate tide gauge | 16:32 | 2.0 m |

TOKU* (25Mhz) | 17:29 | KO* wave gauge | 17:24 | 0.5 m |

ANAN* (25Mhz) | 17:25 | KO* wave gauge | 17:24 | 0.5 m |

US West Coast 11 March 2011 UTC | ||||
---|---|---|---|---|

Radar (XMTR Freq) | Arrival Time (UTC) | Tide Gauge | Arrival Time (UTC) | Water-Level Change |

STV2 (12 MHz) | 15:32 | Garibaldi | 15:48 | 1.2 m |

SEA1 (12 MHz) | 15:47 | Garibaldi | 15:48 | 1.2 m |

YHS2 (12 MHz) | 15:45 | South Beach | 15:54 | 0.3 m |

TRIN (5 MHz) | 15:34 | Crescent City | 15:48 | 0.5 m |

GCVE (14 MHz) | 15:44 | Pt. Reyes | 16:00 | 0.5 m |

BML1 (12 MHz) | 15:46 | Pt. Reyes | 16:00 | 0.5 m |

PREY (13 MHz) | 15:49 | Pt. Reyes | 16:00 | 0.5 m |

COMM (13 MHz) | 15:56 | Fort Point | 16:30 | 0.4 m |

ESTR (13 MHz) | 16:04 | Port San Luis | 16:24 | 2.0 m |

LUIS (13 MHz) | 16:05 | Port San Luis | 16:24 | 2.0 m |

## Share and Cite

**MDPI and ACS Style**

Lipa, B.; Isaacson, J.; Nyden, B.; Barrick, D.
Tsunami Arrival Detection with High Frequency (HF) Radar. *Remote Sens.* **2012**, *4*, 1448-1461.
https://doi.org/10.3390/rs4051448

**AMA Style**

Lipa B, Isaacson J, Nyden B, Barrick D.
Tsunami Arrival Detection with High Frequency (HF) Radar. *Remote Sensing*. 2012; 4(5):1448-1461.
https://doi.org/10.3390/rs4051448

**Chicago/Turabian Style**

Lipa, Belinda, James Isaacson, Bruce Nyden, and Donald Barrick.
2012. "Tsunami Arrival Detection with High Frequency (HF) Radar" *Remote Sensing* 4, no. 5: 1448-1461.
https://doi.org/10.3390/rs4051448