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MQUAKE multicast software early warning demonstrated for 31 October 2001 Anza Ml 5.1 earthquake

SCRI

PPS

INST

ITUTION OF OCEANOGRAPHY

UCSD

J.A. Eakins1, T. Hansen2, F.L. Vernon1, H-W. Braun2

1IGPP, Univ. of California, San Diego, MC-0225 9500 Gilman Drive, La Jolla, CA 92093-0225 2SDSC, Unif. of California, San Diego MC-0505 9500 Gilman Drive, La Jolla, CA 92093-0505

MQUAKE distributes realtime multicast parametric information from individual sensors as well as a summarized location and magnitude based on the data recorded from sensors of the ANZA seismic network with the goal of providing event notification prior to arrival of the actual shock wave at the client's location. The program gathers detection and triggering information from an operational Antelope real-time data collection system and sends them to clients via multicast and unicast UDP packets. Multicast packets are preferred as they allow multiple people to receive event packets in the fastest time possible (however, a unicast mode is available since most IP networks do not yet support multicast). These packets are decrypted in client software which then produces a list of triggers/events that will be used in future versions of the code to generate wavefront estimate plots and approximate maximum shock wave travel times based on the client's location and limited current information. This systems works in both a wired and wireless environment, such as HPWREN, the High Performance Wireless Research and Education Network.

A real-time example of this system was obtained during the Ml5.1 31 October 2001 earthquake that occurred directly under the ANZA seismic network, approximately 70 km away from an MQUAKE client. The MQUAKE program was able to deliver a warning of a significant "event" 10 seconds after the initial ground motion was recorded and about 4 seconds prior to ground motion reaching the client. An actual event location and magnitude approximation was received 71 seconds after the local ground shaking at the client's location (85 seconds after the event). Had the client been located along the coast of San Diego, they would have had additional warning time prior to the shaking. Clients in San Diego, the closest major metropolitan area to this event, could have received up to 12 seconds of early warning.

Abstract:

Toro ORB

seismic sensors

IGPP ORB(located at UCSD)

orbdetect

orbtriggerorbassocorbwfmeas

mquake_sendmulticast UDP packets

unicast UDP packets

Client Event Viewers

<alert>

<alert>

databasevarious remote locations

Operational MQUAKE alert system

Figure 2 shows the seismic data flow and processing involved in generating early warning notifications. Broadband seismometers and strong motion accelerometers continuously collect 100, 40, and 1 sample/second waveform data. These samples are transmitted via spread spectrum radio to Toro Peak where they are buffered in an Antelope ORB (Object Ring Buffer) via software developed by BRTT. The data almost instantaneously (assuming minimal telemetry delays) arrives at UCSD's data processing computer (IGPP ORB). The orbdetect process continuously monitors incoming data for signal to noise changes. In the event of a significant change it generates a notification back to the ring buffer. This notification is recognized by the mquake_send program. mquake_send gathers data from the database related to the station where the detection occurred. The mquake_send program then formats an alert string and sends it out via a multicast UDP packet. Following the dispatch of the multicast packet, it sends a series of UDP unicast packets to other recipients not on a multicast connected network. An application running on the client's computer listens for these packets and if a packet arrives that exceeds a notification threshold, it generates a visual warning and can launch an external application such as a music player.

After a series of these alerts (and usually after the shockwave has passed) a secondary set of programs, running on IGPP ORB (orbtrigger, orbassoc, orbwfmeas), are able to put together an epicenter and magnitude for the earthquake as well as information about peak ground velocity and acceleration. This information is also collected by mquake_send and sent to remote clients to provide additional information about events after the initial alert has been sent.

In future versions, we look forward to providing visual and mathematical elimination to determine more accurately when the leading edge will arrive (as additional sensors report).

HPWREN provides redundancy and bandwidth

Figure 1. HPWREN is the High Performance Wireless Research and Education Network. The HPWREN team is creating, demonstrating and evaluating a high-performance wide-area wireless network in San Diego and Riverside counties. This network brings reliable internet access to remote locations allowing real-time data collection from sensors as well as providing mechanisms for distributing the multicast messages sent from MQUAKE via an IP multicast overlay called MBONE.

San Diego

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Figure 4c - Seismic wave arrival time (sec)

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shook afterwarning

Figure 4. These maps show the epicenter (red star) of the Ml 5.1 October 31, 2001 earthquake that occurred in the middle of the Anza seismic network. The closest station, TRO, was ~6 km away from the source. Colored contours illustrate the arrival times of the P (top) and S (bottom) waves at various seismic sensors in California. The contour interval is 1 second. Where data is sparse, the contours have been deleted. For mapping purposes, both SCSN/CISN and ANZA stations with arrival times are shown, but only ANZA stations were used for detecting the event and generating the MQUAKE alert. Stations are shown as small black circles with arrival times in seconds listed nearby. The inverted purple triangle (HWB) represents an actual MQUAKE client ~68 km from the epicenter. The inverted brown (MONP) and yellow (SOL) triangles indicate locations of selected seismic sensors. See Figure 5 for more details.

The MQUAKE program generated an alert about this event that arrived at HWB 10 seconds after the event occurred. Therefore, any person running an MQUAKE multicast client who was located outside of the orange contour in Figure 4a would have had some warning of approaching ground motion. Maximum shaking occurred with the arrival of the S wave, so an even larger number of people could have received warning of the approaching seismic wave. San Diego is located ~100 km from this active fault and can thus benefit from about 7 seconds of advanced warning of P wave arrival and 19 seconds of warning regarding the S wave arrival.

Figure 4c below shows a scale bar corresponding to the mapped contours and helps illustrate who would receive a multicast warning prior to feeling the seismic wave.

Who would have warning?

Figure 4a - P wave arrival times

Figure 4b - S wave arrival times

Latitude Longitude Origin Time (UTC) Depth (km) Ml33.5083 -116.5143 10/31/2001 (304) 7:56:16.630 15.2200 5.09

S tatio n phase A rriva l Ti me ∆ (deg )T R O P 10/31/2001 (3 04) 7:56 : 19.3 97 0.0 56F RD P 10/31/2001 (3 04) 7:56 : 19.3 22 0.0 95P FO P 10/31/2001 (3 04) 7:56 : 19.5 10 0.0 95SN D P 10/31/2001 (3 04) 7:56 : 19.6 00 0.1 05B ZN P 10/31/2001 (3 04) 7:56 : 19.9 97 0.1 49WMC P 10/31/2001 (3 04) 7:56 : 20.2 81 0.1 61L VA 2 P 10/31/2001 (3 04) 7:56 : 20.5 44 0.1 79CR Y P 10/31/2001 (3 04) 7:56 : 20.9 00 0.2 09KNW P 10/31/2001 (3 04) 7:56 : 21.7 70 0.2 66RD M P 10/31/2001 (3 04) 7:56 : 22.5 09 0.3 16MO NP P 10/31/2001 (3 04) 7:56 : 28.2 74 0.6 31T HSB P 10/31/2001 (3 04) 7:56 : 32.1 88 0.8 89S OL P 10/31/2001 (3 04) 7:56 : 33.0 40 0.9 29S tatio n phase A rriva l Ti me ∆ (deg )T R O S 10/31/2001 (3 04) 7:56 : 21.8 55 0.0 56F RD S 10/31/2001 (3 04) 7:56 : 21.7 37 0.0 95P FO S 10/31/2001 (3 04) 7:56 : 21.9 51 0.0 95SN D S 10/31/2001 (3 04) 7:56 : 22.3 90 0.1 05B ZN S 10/31/2001 (3 04) 7:56 : 22.9 84 0.1 49WMC S 10/31/2001 (3 04) 7:56 : 23.5 07 0.1 61L VA 2 S 10/31/2001 (3 04) 7:56 : 23.7 43 0.1 79CR Y S 10/31/2001 (3 04) 7:56 : 24.3 60 0.2 09KNW S 10/31/2001 (3 04) 7:56 : 25.8 42 0.2 66RD M S 10/31/2001 (3 04) 7:56 : 27.3 33 0.3 16MO NP S 10/31/2001 (3 04) 7:56 : 36.9 80 0.6 31RS B S 10/31/2001 (3 04) 7:56 : 42.0 96 0.8 28T HSB S 10/31/2001 (3 04) 7:56 : 43.5 28 0.8 89S OL S 10/31/2001 (3 04) 7:56 : 44.9 63 0.9 29

07:56:20.0002001304

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69 km

101 km

EventAutomatic

location

(event + 85sec)

MQUAKE

alarm

(event + 10sec)

Figure 5. Vertical components recorded by broadband sensors at two potential MQUAKE client locations (actual client was ~68km from event source). Inverted triangles correspond to station locations shown on the map in figure 4. The vertical red line indicates time of event. Response time of MQUAKE (arrival time of 'event warning' at MONP and SOL) is indicated by the purple line. Arrival time at client of automatic event solution (location and magnitude) is indicated by the green line, approximately 55 seconds after maximum shaking began at SOL (major populated area - San Diego). Colored flags indicate P and S arrival times shown with a color scale matching that of the contours in Figure 4.

Maximum shaking at station SOL starts approximately 29 seconds after the event initiated. An MQUAKE warning arrives within 10 seconds of the event, giving 7 seconds of advanced warning (19 seconds warning before maximum shaking).

MQUAKE acts as an early warning system when an information alert simply outruns a shockwave to aclient's location.

MQUAKE utilizes multicast where available to alert multiple people as quickly as possible.

Unicast UDP is also supported to alert people who are not multicast connected.

Alerts may be a visual message on a CRT or a sound played out of a computer speaker.

MQUAKE currently interfaces with the Antelope real-time system.

The MQUAKE client application can run on multiple platforms (windows, linux, freebsd, solaris).

The client application can set an alert threshold so users only get notified about what interests them.

Additional event summary information (magnitude and location) is provided after the initial warning to provide further details about the event.

What is MQUAKE?

Can only warn about an event that has already started and been detected by the local seismic network.

Telemetry delays in the seismic network could be problematic. However excess bandwidth can makerecovery from outages quicker. Still systems that deliberately queue data before sending will incuradded latency in their warnings.

It cannot outrun all earthquakes (like those that occur closer to the client’s location than to the sensor network).

Current version of the code is based upon signal-to-noise event detections but better amplitude detectorsare needed.

Orbwfmeas, the program which gathers true amplitude measurements, is too slow for an early warning system.

Limitations of MQUAKE

A visualization system that shows where the detections occurred relative to a client and also calculates themaximum time before the shockwaves arrive.

Initial warnings will include approximate velocity/acceleration at sensor locations, allowing for better filtering.

Hazard mapping by client location: indicate possible earthquake source areas where MQUAKE will not be able toalert the client in advance of ground shaking.

Other notification protocols.

Geographical thresholding, so clients can choose not to worry about events that are > X miles from their location.

Better optimize true amplitude measurements for use in early warning.

Proposed future developments

Alert generated for 31 October 2001 earthquake

Figure 3. Testing of the MQUAKE program on an active real-time system began during the summer of 2001. At 07:54 (UTC) on October 31, 2001, a client received an alert message and soon felt the Ml 5.1 earthquake. (a) Location, time and magnitude for the event are listed below. (b) The figure on the right shows the actual signal as depicted by the orbmonrtd program. Station names are shown at the left side of the figure. Each yellow trace represents the vertical component recorded at a single station. The scaling is such that many stations appear to have clipped, but when the raw seismic data is viewed, only three broadband sensors had clipped records. The client who received the MQUAKE alert was located at approximately the same distance from the source as station AZ_MONP_HHZ and received about 4 seconds of warning of impending gound motion. (c) To the right of the traces is a table listing arrival times for ANZA network stations.

(3a)

(3b) (3c)(3c)