http://docs.codehaus.org/display/JETTY/Maven+Jetty+Plugin
http://logback.qos.ch/faq.html#setup_jetty

You should add the following or something similar to the FAQ:

pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
...
<build>
...
<plugins>
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
<configuration>
...
<systemProperties>
<systemProperty>
<name>logback.configurationFile</name>
<value>./src/etc/logback.xml</value>
</systemProperty>
</systemProperties>
</configuration>
<dependencies>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>${lb.version}</version>
</dependency>
...
</dependencies>
</plugin>
</plugins>
</build>
<properties>
<lb.version>0.9.15</lb.version>
</properties>
</project>

If one just adds the dependency on logback-classic the BasicConfigurator will be used for Jetty, resulting in a lot of debug statements.

The important part is the systemProperty.

You might want to update the example at http://svn.qos.ch/repos/logback-demo/tags/STABLE also.